page_content stringlengths 12 2.63M | metadata unknown |
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| <b>Protein Component</b> | Prosthetic Groups* |
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| NADH-CoQ reductase<br>(complex I) | FMN<br>Fe-S ... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
However, the net charge of each Fe atom is actually between +2 and +3 because electrons in the outermost orbits are dispersed among the Fe atoms and move rapidly from one atom to another. Iron-sulfur clusters accept and release electrons one at a time; the additional electron is also dispersed over all the Fe atoms in ... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
Because of its long hydrocarbon "tail" of isoprene units, CoQ is soluble in the hydrophobic core of phospholipid bilayers and is very mobile. Reduction of CoQ to the fully reduced form, $QH_2$ , occurs in two steps with a half-reduced free-radical intermediate, called *semiquinone*.
▲ ... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
As we saw in Chapter 2, the **reduction potential** $\boldsymbol{E}$ for a partial reduction reaction
is a measure of the equilibrium constant of that partial reaction. With the exception of the b cytochromes in the $CoQH_2$ -cytochrome c reductase complex, the standard reduction potential $E^{\circ\prime}$ of t... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
Experiments like the one depicted in Figure 8-19 have shown that four protons are translocated across the membrane per electron pair transported from $CoQH_2$ through the $CoQH_2$ -cytochrome c reductase complex. Thus this complex transports two protons per electron transferred, whereas the cytochrome c oxidase comp... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
Movement of the hinge then positions the 2Fe-2S cluster near enough to the heme on cytochrome *c*<sup>1</sup> for electron transfer to occur. With the Fe-S subunit in this alternative conformation, the second electron released from CoQH2 bound to the Qo site cannot move to the 2Fe-2S cluster and has to take the less th... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
Thus the $F_0$ **a** and **b** subunits and the $F_1$ $\delta$ subunit and $(\alpha\beta)_3$ hexamer form a rigid structure anchored in the membrane (orange). During proton flow, the **c** ring and the attached $F_1 \varepsilon$ and $\gamma$ subunits rotate as a unit (green), causing conformation changes in ... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
This generates an $F_1$ complex identical with that which started the process (left) except that it is rotated 120°. Step $\ref{3}$ : Another 120° rotation of $\gamma$ again causes the $O \to L \to T \to O$ conformational changes in the $\beta$ subunits described above. Repetition of steps $\ref{3}$ and $\r... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
This exchange, which is required for oxidative phosphorylation to continue, is mediated by two proteins in the inner membrane: a *phosphate transporter* (HPO4 <sup>2</sup>/OH antiporter) and an *ATP/ADP antiporter* (Figure 8-28)*.*
▲ **FIGURE 8-28 The phosphate and ATP/ADP transport sy... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
We now shift our attention to photosynthesis, the second main process for synthesizing ATP. Photosynthesis in plants occurs in chloroplasts, large organelles found mainly in leaf cells. The principal end products are two carbohydrates that are polymers of hexose (six-carbon) sugars; sucrose, a glucose-fructose disaccha... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
Chloroplasts are bounded by two membranes, which do not contain chlorophyll and do not participate directly in photosynthesis (Figure 8-30). As in mitochondria, the outer membrane of chloroplasts contains porins and thus is permeable to metabolites of small molecular weight. The inner membrane forms a permeability barr... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
The photosynthetic process in plants can be divided into four stages, each localized to a defined area of the chloroplast: (1) absorption of light, (2) electron transport leading to formation of $O_2$ from $H_2O$ , reduction of NADP<sup>+</sup> to NADPH, and generation of a proton-motive force, (3) synthesis of ATP,... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
Quantum mechanics established that light, a form of electromagnetic radiation, has properties of both waves and particles. When light interacts with matter, it behaves as discrete packets of energy (quanta) called *photons*. The energy of a photon, $\varepsilon$ , is proportional to the frequency of the light wave: $... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
The absorption of light energy and its conversion into chemical energy occurs in multiprotein complexes called **photosystems**. Found in all photosynthetic organisms, both eukaryotic and prokaryotic, photosystems consist of two closely linked components: a *reaction center*, where the primary events of photosynthesis ... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
The absorption of a photon of light of wavelength $\approx$ 680 nm by chlorophyll a increases its energy by 42 kcal/mol (the first excited state). Such an energized chlorophyll a molecule in a plant reaction center rapidly donates an electron to an intermediate acceptor, and the electron is rapidly passed on to the pr... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
Although chlorophyll *a* molecules within a reaction center are capable of directly absorbing light and initiating photosynthesis, they most commonly are energized indirectly by energy transferred from light-harvesting complexes (LHCs) in an associated antenna. Even at the maximum light intensity encountered by photosy... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
As noted in the previous section, photosynthesis in the green and purple bacteria does not generate oxygen, whereas photosynthesis in cyanobacteria, algae, and higher plants does.\* This difference is attributable to the presence of two types of photosystem (PS) in the latter organisms: PSI reduces NADP<sup>+</sup> to ... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
(*Center*) After diffusing through the membrane and binding to the $Q_O$ site on the
exoplasmic face of the cytochrome $bc_1$ complex, $QH_2$ donates two electrons and simultaneously gives up two protons to the external medium, generating a proton-motive force ( $H^+_{exoplasmic}$ ). Electrons are transported b... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
Somewhat surprisingly, the structure of the PSII reaction center, which removes electrons from $H_2O$ to form $O_2$ , resembles that of the reaction center of photosynthetic purple bacteria, which does not form $O_2$ . Like the bacterial reaction center, the PSII reaction center contains two molecules of chlorophyl... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
As we've seen, electrons from reduced ferredoxin in PSI are transferred to NADP<sup>+</sup> during linear electron flow (see Figure 8-37). Alternatively, reduced ferredoxin can donate two electrons to a quinone (Q) bound to a site on the stromal surface of PSI; the quinone then picks up two protons from the stroma, for... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
In order for PSII and PSI to act in sequence during linear electron flow, the amount of light energy delivered to the two reaction centers must be controlled so that each center activates the same number of electrons. If the two photosystems are not equally excited, then cyclic electron flow occurs in PSI, and PSII bec... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
PLANTS
Chloroplasts perform many metabolic reactions in green leaves. In addition to $CO_2$ fixation, the synthesis of almost all amino acids, all fatty acids
and carotenes, all pyrimidines, and probably all purines occurs in chloroplasts. However, the synthesis of sugars from $CO_2$ is the most extensively stu... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
$$\begin{array}{c} \mathsf{CH}_2 - \mathsf{O} - \mathsf{PO}_3 \mathsf{H}^- \\ \mathsf{CH}_2 - \mathsf{O} - \mathsf{PO}_3 \mathsf{H}^- \\ \mathsf{C} - \mathsf{O} \\ \mathsf{H} - \mathsf{C} - \mathsf{OH} \\ \mathsf{H} - \mathsf{C} - \mathsf{OH} \\ \mathsf{CH}_2 - \mathsf{O} - \mathsf{PO}_3 \mathsf{H}^- \\ \mathsf{H} - ... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
After its formation in the chloroplast stroma, glyceraldehyde 3-phosphate is transported to the cytosol in exchange for phosphate. The final steps of sucrose synthesis occur in the cytosol of leaf cells. In these reactions, one molecule of glyceraldehyde 3-phosphate is isomerized to dihydroxyacetone phosphate. This com... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
The Calvin cycle enzymes that catalyze $\mathrm{CO}_2$ fixation are rapidly inactivated in the dark, thereby conserving ATP that is generated in the dark for other synthetic reactions, such as lipid and amino acid biosynthesis. One mechanism that contributes to this control is the pH dependence of several
Calvin cy... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
Photosynthesis is always accompanied by **photorespiration**—a process that takes place in light, consumes $O_2$ , and converts ribulose 1,5-bisphosphate in part to $CO_2$ . As Figure 8-43 shows, rubisco catalyzes two competing reactions: the addition of $CO_2$ to ribulose 1,5-bisphosphate to form two molecules of ... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
Sieve-tube cells have lost their nuclei and most other organelles but retain a water-permeable plasma membrane and cytoplasm, through which sucrose and water move. In effect, the sievetube cells form one continuous tube of cytosol that extends throughout the plant. Differences in osmotic strength cause the movement of ... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
- **a.** When these vesicles were incubated in a physiological buffer containing NADH, ADP, Pi, and O2, the fluorescence of BCECF trapped inside gradually decreased in intensity. What does this decrease in fluorescent intensity suggest about this vesicular preparation?
- **b.** How woul... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
Sci.* **27**:154–160.
Elston, T., H. Wang, and G. Oster. 1998. Energy transduction in ATP synthase. *Nature* **391**:510–512.
Kinosita, K., et al. 1998. F1-ATPase: a rotary motor made of a single molecule. *Cell* **93**:21–24.
Klingenberg, M., and S. Huang. 1999. Structure and function of the uncoupling protein f... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
The effect of mutations on *Drosophila* development. Scanning electron micrographs of the eye from (*left*) a wild-type fly, (*middle*) a fly carrying a dominant developmental mutation produced by recombinant DNA methods, an... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
A fundamental genetic difference between experimental organisms is whether their cells carry a single set of chromosomes or two copies of each chromosome. The former are referred to as **haploid**; the latter, as **diploid**. Complex multicellular organisms (e.g., fruit flies, mice, humans) are diploid, whereas many si... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
Haploid yeast cells, which carry one copy of each chromosome, can be of two different mating types known as **a** and -*.* Haploid cells of opposite mating type can mate to produce **a**/ diploids, which carry two copies of each chromosome. If a new mutation with an observable phenotype is isolated in a haploid strain,... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
The procedures used to identify and isolate mutants, referred to as *genetic screens*, depend on whether the experimental organism is haploid or diploid and, if the latter, whether the mutation is recessive or dominant. Genes that encode proteins essential for life are among the most interesting and important ones to s... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
Based on careful analysis of mutant phenotypes associated with a particular cellular process, researchers often can deduce the order in which a set of genes and their protein products function. Two general types of processes are amenable to such analysis: (a) biosynthetic pathways in which a precursor material is conve... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
The phenotypes associated with dominant mutations often represent a gain of function but in the case of some genes result from a loss of function.
- In meiosis, a diploid cell undergoes one DNA replication and two cell divisions, yielding four haploid cells in which maternal and paternal alleles are randomly assorted (... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
**Plasmids** are circular, double-stranded DNA (dsDNA) molecules that are separate from a cell's chromosomal DNA. These extrachromosomal DNAs, which occur naturally in bacteria and in lower eukaryotic cells (e.g., yeast), exist in a parasitic or symbiotic relationship with their host cell. Like the host-cell chromosoma... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
It is technically feasible to use phage cloning vectors to generate a *genomic library,* that is, a collection of clones that collectively represent all the DNA sequences in the genome of a particular organism. However, such genomic libraries for higher eukaryotes present certain experimental difficulties. First, the... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
Both genomic and cDNA libraries of various organisms contain hundreds of thousands to upwards of a million individual clones in the case of higher eukaryotes. Two general approaches are available for screening libraries to identify clones carrying a gene or other DNA region of interest: (1) detection with oligonucleoti... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
In some cases a DNA library can be screened for the ability to express a functional protein that complements a recessive mutation. Such a screening strategy would be an efficient way to isolate a cloned gene that corresponds to an interesting recessive mutation identified in an experimental organism. To illustrate this... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
As a result, when the gel is illuminated with ultraviolet light, the regions of the gel containing DNA fluoresce much more brightly than the regions of the gel without DNA.
Once a cloned DNA fragment, especially a long one, has been separated from vector DNA, it often is treated with various restriction enzymes to yi... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
If the nucleotide sequences at the ends of a particular DNA region are known, the intervening fragment can be amplified directly by the **polymerase chain reaction (PCR)**. Here we describe the basic PCR technique and three situations in which it is used.
The PCR depends on the ability to alternately denature (melt) ... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
(The blot is used because probes do not readily diffuse into the original gel.) The filter then is incubated under hybridization conditions with a specific radiolabeled DNA probe, which usually is generated from a cloned restriction frag-
▲ **EXPERIMENTAL FIGURE 9-27 Northern blot analy... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
(a) In transient transfection, the plasmid vector contains an origin of replication for a virus that can replicate in the cultured animal cells. Since the vector is not incorporated into the genome of the cultured cells, production of the cDNAencoded protein continues only for a limited time. (b) In stable transfection... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
Even when a protein shows no significant similarity to other proteins with the BLAST algorithm, it may nevertheless share a short sequence with other proteins that is functionally important Such short segments recurring in many different proteins, referred to as **motifs**, generally have similar functions. Several s... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
The complete genomic sequence of an organism contains within it the information needed to deduce the sequence of every protein made by the cells of that organism. For organisms such as bacteria and yeast, whose genomes have few introns and short intergenic regions, most protein-coding
sequences can be found simply by... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
The relative intensities of red and green fluorescence signals at each spot are a measure of the relative level of expression of that gene in cells grown in glucose or ethanol. Genes that are not transcribed under these growth conditions give no detectable signal.
Hybridization of fluorescently labeled cDNA preparati... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
construct for disrupting a target gene can be prepared by the PCR. The two primers designed for this purpose each contain a sequence of about 20 nucleotides (nt) that is homologous to one end of the target yeast gene as well as sequences needed to amplify a segment of DNA carrying a selectable marker gene such as *kanM... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
Although disruption of an essential gene required for cell growth will yield nonviable spores, this method provides little information about what the encoded protein actually does in cells. To learn more about how a specific gene contributes to cell growth and viability, investigators must be able to selectively inacti... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
However, mice car-
#### ▲ **EXPERIMENTAL FIGURE 9-40 The** *loxP-Cre*
**recombination system can knock out genes in specific cell types.** Two *loxP* sites are inserted on each side of an essential exon (2) of the target gene *X* (blue) by homologous recombination, producing a *loxP* ... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
Researchers are exploiting a recently discovered phenomenon known as **RNA interference (RNAi)** to inhibit the function of specific genes. This approach is technically simpler than the methods described above for disrupting genes. First observed in the roundworm *C. elegans,* RNAi refers to the ability of a double-str... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
- Once a gene has been cloned, important clues about its normal function in vivo can be deduced from the observed phenotypic effects of mutating the gene.
- Genes can be disrupted in yeast by inserting a selectable marker gene into one allele of a wild-type gene via homologous recombination, producing a heterozygous mu... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
A recessive allele on the X-chromosome will most often be expressed in males, who receive only one X chromosome from their mother, but not in females who receive an X chromosome from both their mother and father. This leads to a distinctive sex-linked segregation pattern where the disease is exhibited much more frequen... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
The more families exhibiting a particular disease that can be examined, the greater the statistical significance of evidence for linkage that can be obtained and the greater the precision with which the distance can be measured between a linked DNA polymorphism and a disease allele. Most family studies have a maximum o... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
By examining the phenotypic consequences of mutations that inactivate a particular gene, geneticists are able to connect knowledge about the sequence, structure, and biochemical activity of the encoded protein to its function in the context of a living cell or multicellular organism. The classical approach to making th... | {
"Header 1": "▲ FIGURE 8-12 Allosteric control of glucose metabolism in the cytosol at the level of fructose 6-phosphate. The key regulatory enzyme in glycolysis, phosphofructokinase-1, is allosterically activated by AMP and fructose 2,6-bisphosphate, which are elevated when the cell's energy stores are low. The enz... |
c. To investigate the role of proteins p24 and p25 for viral replication in live mice, transgenic mice that lack genes for p24 or p25 are generated. The *loxP*-Cre conditional knockout system is used to selectively delete the genes in cells of either the liver or the lung. Wild type and knockout mice are infected with ... | {
"Header 1": "$\\begin{array}{lll} \\textbf{Cell Treatment} & \\textbf{Number of Viruses/ml} \\\\ \\textbf{Control} & 1\\times 10^7 \\\\ \\textbf{siRNA-p24} & 3\\times 10^6 \\\\ \\textbf{siRNA-p25} & 2\\times 10^6 \\\\ \\textbf{siRNA-p24} & \\textbf{and siRNA-p25} & 1\\times 10^4 \\\\ \\textbf{siRNA to viral protein... |
Altering the genome by homologous recombination. *Science* **244**:1288–1292.
Deshaies, R. J., et al. 1988. A subfamily of stress proteins facilitates translocation of secretory and mitochondrial precursor polypeptides. *Nature* **332**:800–805.
Fire, A., et al. 1998. Potent and specific genetic interference by dou... | {
"Header 1": "$\\begin{array}{lll} \\textbf{Cell Treatment} & \\textbf{Number of Viruses/ml} \\\\ \\textbf{Control} & 1\\times 10^7 \\\\ \\textbf{siRNA-p24} & 3\\times 10^6 \\\\ \\textbf{siRNA-p25} & 2\\times 10^6 \\\\ \\textbf{siRNA-p24} & \\textbf{and siRNA-p25} & 1\\times 10^4 \\\\ \\textbf{siRNA to viral protein... |
These brightly colored RxFISH-painted chromosomes are both beautiful and useful in revealing chromosome anomalies and in comparing karyotypes of different species. [© Department of Clinical Cytogenetics, Addenbrookes Hospital/Photo Researchers, Inc.]
biologists had completed sequencing ... | {
"Header 1": "$\\begin{array}{lll} \\textbf{Cell Treatment} & \\textbf{Number of Viruses/ml} \\\\ \\textbf{Control} & 1\\times 10^7 \\\\ \\textbf{siRNA-p24} & 3\\times 10^6 \\\\ \\textbf{siRNA-p25} & 2\\times 10^6 \\\\ \\textbf{siRNA-p24} & \\textbf{and siRNA-p25} & 1\\times 10^4 \\\\ \\textbf{siRNA to viral protein... |
The cluster of genes that form a bacterial operon comprises a single **transcription unit**, which is transcribed from a particular promoter into a single primary transcript. In other words, genes and transcription units often are distinguish-
► FIGURE 10-2 Comparison of simple and complex eukaryotic transcription un... | {
"Header 1": "$\\begin{array}{lll} \\textbf{Cell Treatment} & \\textbf{Number of Viruses/ml} \\\\ \\textbf{Control} & 1\\times 10^7 \\\\ \\textbf{siRNA-p24} & 3\\times 10^6 \\\\ \\textbf{siRNA-p25} & 2\\times 10^6 \\\\ \\textbf{siRNA-p24} & \\textbf{and siRNA-p25} & 1\\times 10^4 \\\\ \\textbf{siRNA to viral protein... |
Having reviewed the relation between transcription units and genes, we now consider the organization of genes on chromosomes and the relationship of noncoding DNA sequences to coding sequences.
#### Genomes of Many Organisms Contain Much Nonfunctional DNA
Comparisons of the total chromosomal DNA per cell in various... | {
"Header 1": "$\\begin{array}{lll} \\textbf{Cell Treatment} & \\textbf{Number of Viruses/ml} \\\\ \\textbf{Control} & 1\\times 10^7 \\\\ \\textbf{siRNA-p24} & 3\\times 10^6 \\\\ \\textbf{siRNA-p25} & 2\\times 10^6 \\\\ \\textbf{siRNA-p24} & \\textbf{and siRNA-p25} & 1\\times 10^4 \\\\ \\textbf{siRNA to viral protein... |
As shown in Figure 10-3a, the -like globin gene family contains five functional genes designated , , A, G, and ; the encoded polypeptides are similarly designated. Two identical -like globin polypeptides combine with two identical -globin polypeptides (encoded by another gene family) and four small heme groups to form ... | {
"Header 1": "$\\begin{array}{lll} \\textbf{Cell Treatment} & \\textbf{Number of Viruses/ml} \\\\ \\textbf{Control} & 1\\times 10^7 \\\\ \\textbf{siRNA-p24} & 3\\times 10^6 \\\\ \\textbf{siRNA-p25} & 2\\times 10^6 \\\\ \\textbf{siRNA-p24} & \\textbf{and siRNA-p25} & 1\\times 10^4 \\\\ \\textbf{siRNA to viral protein... |
In vertebrates and invertebrates, the genes encoding rRNAs and some other noncoding RNAs such as some of the snRNAs involved in RNA splicing occur as *tandemly repeated arrays*. These are distinguished from the duplicated genes of gene families in that the multiple tandemly repeated genes encode identical or nearly ide... | {
"Header 1": "$\\begin{array}{lll} \\textbf{Cell Treatment} & \\textbf{Number of Viruses/ml} \\\\ \\textbf{Control} & 1\\times 10^7 \\\\ \\textbf{siRNA-p24} & 3\\times 10^6 \\\\ \\textbf{siRNA-p25} & 2\\times 10^6 \\\\ \\textbf{siRNA-p24} & \\textbf{and siRNA-p25} & 1\\times 10^4 \\\\ \\textbf{siRNA to viral protein... |
Even slight differences in the total lengths of various minisatellites from different individuals can be detected by **Southern blotting** of cellular DNA treated with a restriction enzyme that cuts outside the repeat sequence (Figure 10-7). The polymerase chain reaction (PCR), using
primers that hybridize to the uni... | {
"Header 1": "$\\begin{array}{lll} \\textbf{Cell Treatment} & \\textbf{Number of Viruses/ml} \\\\ \\textbf{Control} & 1\\times 10^7 \\\\ \\textbf{siRNA-p24} & 3\\times 10^6 \\\\ \\textbf{siRNA-p25} & 2\\times 10^6 \\\\ \\textbf{siRNA-p24} & \\textbf{and siRNA-p25} & 1\\times 10^4 \\\\ \\textbf{siRNA to viral protein... |
Most mobile elements in bacteria transpose directly as DNA. In contrast, most mobile elements in eukaryotes are retrotransposons, but eukaryotic DNA transposons also occur. Indeed, the original mobile elements discovered by Barbara McClintock are DNA transposons.
Bacterial Insertion Sequences The first molecular unde... | {
"Header 1": "$\\begin{array}{lll} \\textbf{Cell Treatment} & \\textbf{Number of Viruses/ml} \\\\ \\textbf{Control} & 1\\times 10^7 \\\\ \\textbf{siRNA-p24} & 3\\times 10^6 \\\\ \\textbf{siRNA-p25} & 2\\times 10^6 \\\\ \\textbf{siRNA-p24} & \\textbf{and siRNA-p25} & 1\\times 10^4 \\\\ \\textbf{siRNA to viral protein... |
The genomes of all eukaryotes studied from yeast to humans contain retrotransposons, mobile DNA elements that transpose through an RNA intermediate utilizing a reverse transcriptase (see Figure 10-8b). These mobile elements are divided into two major categories, those containing and those lacking long terminal repeats ... | {
"Header 1": "$\\begin{array}{lll} \\textbf{Cell Treatment} & \\textbf{Number of Viruses/ml} \\\\ \\textbf{Control} & 1\\times 10^7 \\\\ \\textbf{siRNA-p24} & 3\\times 10^6 \\\\ \\textbf{siRNA-p25} & 2\\times 10^6 \\\\ \\textbf{siRNA-p24} & \\textbf{and siRNA-p25} & 1\\times 10^4 \\\\ \\textbf{siRNA to viral protein... |
The general structure of LTR retrotransposons found in eukaryotes is depicted in Figure 10-11. In addition to short 5′ and 3′ direct repeats typical of all mobile elements, these retrotransposons are marked by the presence of LTRs flanking the central protein-coding region. These *l*ong direct terminal repeats, contain... | {
"Header 1": "▲ FIGURE 10-11 General structure of eukaryotic LTR retrotransposons. The central protein-coding region is flanked by two long terminal repeats (LTRs), which are element-specific direct repeats. Like other mobile elements, integrated retrotransposons have short target-site direct repeats at each end. No... |
▼ FIGURE 10-13 Model for reverse transcription of retroviral genomic RNA into DNA. In this model, a complicated series of nine events generates a double-stranded DNA copy of the single-stranded RNA genome of a retrovirus (top). The genomic RNA is packaged in the virion with a retrovirus-s... | {
"Header 1": "▲ FIGURE 10-12 Generation of retroviral genomic RNA from integrated retroviral DNA. The left LTR directs cellular RNA polymerase II to initiate transcription at the first nucleotide of the left R region. The resulting primary transcript extends beyond the right LTR. The right LTR, now present in the RN... |
The most abundant mobile elements in mammals are retrotransposons that lack LTRs, sometimes called *nonviral retro*transposons. These moderately repeated DNA sequences form two classes in mammalian genomes: long interspersed elements (LINEs) and short interspersed elements (SINEs). In humans, full-length LINEs are ≈6 k... | {
"Header 1": "▲ FIGURE 10-12 Generation of retroviral genomic RNA from integrated retroviral DNA. The left LTR directs cellular RNA polymerase II to initiate transcription at the first nucleotide of the left R region. The resulting primary transcript extends beyond the right LTR. The right LTR, now present in the RN... |
DNA. The length of the target-site direct repeats varies among copies of the element at different sites in the genome. Although the full-length L1 sequence is ≈6 kb long, variable amounts of the left end are absent at over 90 percent of the sites where this mobile element is found. The shorter open reading frame (ORF1)... | {
"Header 1": "▲ FIGURE 10-12 Generation of retroviral genomic RNA from integrated retroviral DNA. The left LTR directs cellular RNA polymerase II to initiate transcription at the first nucleotide of the left R region. The resulting primary transcript extends beyond the right LTR. The right LTR, now present in the RN... |
In lineages leading to higher eukaryotes, homologous recombination between mobile DNA elements dispersed throughout ancestral genomes may have generated gene duplications and other DNA rearrangements during evolution (see Figure 10-4). For instance, cloning and sequencing of the -globin gene cluster from various prim... | {
"Header 1": "▲ FIGURE 10-12 Generation of retroviral genomic RNA from integrated retroviral DNA. The left LTR directs cellular RNA polymerase II to initiate transcription at the first nucleotide of the left R region. The resulting primary transcript extends beyond the right LTR. The right LTR, now present in the RN... |
When the DNA from eukaryotic nuclei is isolated in isotonic buffers (i.e., buffers with the same salt concentration found in cells, $\approx 0.15$ M KCl), it is associated with an equal mass
of protein as chromatin. The general structure of chromatin has been found to be remarkably similar in the cells of all eukar... | {
"Header 1": "▲ FIGURE 10-12 Generation of retroviral genomic RNA from integrated retroviral DNA. The left LTR directs cellular RNA polymerase II to initiate transcription at the first nucleotide of the left R region. The resulting primary transcript extends beyond the right LTR. The right LTR, now present in the RN... |
When chromatin is extracted from nuclei and examined in the electron microscope, its appearance depends on the salt concentration to which it is exposed. At low salt concentration in the absence of divalent cations such as $\mathrm{Mg}^{+2}$ , isolated chromatin resembles "beads on a string" (Figure 10-19a). In this e... | {
"Header 1": "▲ FIGURE 10-12 Generation of retroviral genomic RNA from integrated retroviral DNA. The left LTR directs cellular RNA polymerase II to initiate transcription at the first nucleotide of the left R region. The resulting primary transcript extends beyond the right LTR. The right LTR, now present in the RN... |
These results indicate that the chromatin structure of nontranscribed DNA is more condensed, and therefore more protected from DNase digestion, than that of transcribed DNA. In condensed chromatin, the DNA is largely inaccessible to DNase I because of its close association with histones and other less abundant chromati... | {
"Header 1": "▲ FIGURE 10-12 Generation of retroviral genomic RNA from integrated retroviral DNA. The left LTR directs cellular RNA polymerase II to initiate transcription at the first nucleotide of the left R region. The resulting primary transcript extends beyond the right LTR. The right LTR, now present in the RN... |
The total mass of the histones associated with DNA in chromatin is about equal to that of the DNA. Interphase chro-
matin and metaphase chromosomes also contain small amounts of a complex set of other proteins. For instance, a growing list of DNA-binding **transcription factors** have been identified associated with ... | {
"Header 1": "▲ FIGURE 10-12 Generation of retroviral genomic RNA from integrated retroviral DNA. The left LTR directs cellular RNA polymerase II to initiate transcription at the first nucleotide of the left R region. The resulting primary transcript extends beyond the right LTR. The right LTR, now present in the RN... |
Certain dyes selectively stain some regions of metaphase chromosomes more intensely than other regions, producing characteristic banding patterns that are specific for individual chromosomes. Although the molecular basis for the regularity of chromosomal bands remains unknown, they serve as useful visible landmarks alo... | {
"Header 1": "▲ FIGURE 10-12 Generation of retroviral genomic RNA from integrated retroviral DNA. The left LTR directs cellular RNA polymerase II to initiate transcription at the first nucleotide of the left R region. The resulting primary transcript extends beyond the right LTR. The right LTR, now present in the RN... |
The dark-staining areas, termed **heterochromatin,** are regions of condensed chromatin. The light-staining, less condensed portions of chromatin are called **euchromatin.** Heterochromatin appears most frequently—but not exclusively—at the centromere and telomeres of chromosomes and is mostly simple-sequence DNA.
In... | {
"Header 1": "▲ FIGURE 10-12 Generation of retroviral genomic RNA from integrated retroviral DNA. The left LTR directs cellular RNA polymerase II to initiate transcription at the first nucleotide of the left R region. The resulting primary transcript extends beyond the right LTR. The right LTR, now present in the RN... |
Region II, although variable in sequence, is fairly constant in length and is rich in A and T
residues. (b) One *Drosophila* simple-sequence DNA located near the centromere has a repeat unit with some homology to the yeast consensus CEN, including two identical 4-bp and 6-bp stretches (red). [See L. Clarke and J. Car... | {
"Header 1": "▲ FIGURE 10-12 Generation of retroviral genomic RNA from integrated retroviral DNA. The left LTR directs cellular RNA polymerase II to initiate transcription at the first nucleotide of the left R region. The resulting primary transcript extends beyond the right LTR. The right LTR, now present in the RN... |
#### 10.6 Organelle DNAs
Although the vast majority of DNA in most eukaryotes is found in the nucleus, some DNA is present within the mitochondria of animals, plants, and fungi and within the chloroplasts of plants. These organelles are the main cellular sites for ATP formation, during oxidative phosphorylation in ... | {
"Header 1": "▲ FIGURE 10-12 Generation of retroviral genomic RNA from integrated retroviral DNA. The left LTR directs cellular RNA polymerase II to initiate transcription at the first nucleotide of the left R region. The resulting primary transcript extends beyond the right LTR. The right LTR, now present in the RN... |
Unlike animal, yeast, and fungal mtDNAs, plant mtDNAs contain genes encoding a 5S mitochondrial rRNA, which is present only in the mitochondrial ribosomes of plants, and the $\alpha$ subunit of the $F_1$ ATPase. The mitochondrial rRNAs of plants are also considerably larger than those of other eukaryotes. Long, non... | {
"Header 1": "▲ FIGURE 10-12 Generation of retroviral genomic RNA from integrated retroviral DNA. The left LTR directs cellular RNA polymerase II to initiate transcription at the first nucleotide of the left R region. The resulting primary transcript extends beyond the right LTR. The right LTR, now present in the RN... |
A third condition, causing "ragged" muscle fibers (with improperly assembled mitochondria) and associated uncontrolled jerky movements, is due to a single mutation in the TCG loop of the mitochondrial lysine tRNA. As a result of this mutation, the translation of several mitochondrial proteins apparently is inhibited ❚ ... | {
"Header 1": "▲ FIGURE 10-12 Generation of retroviral genomic RNA from integrated retroviral DNA. The left LTR directs cellular RNA polymerase II to initiate transcription at the first nucleotide of the left R region. The resulting primary transcript extends beyond the right LTR. The right LTR, now present in the RN... |
Contrast the mechanism of transposition between retrotransposons that contain and those that lack long terminal repeats (LTRs).
- **6.** Describe the role that mobile DNA elements may have played in the evolution of modern organisms. What is the process known as exon shuffling, and what role do mobile DNA elements play... | {
"Header 1": "▲ FIGURE 10-12 Generation of retroviral genomic RNA from integrated retroviral DNA. The left LTR directs cellular RNA polymerase II to initiate transcription at the first nucleotide of the left R region. The resulting primary transcript extends beyond the right LTR. The right LTR, now present in the RN... |
2000. Transcription and replication of mitochondrial DNA. *Hum. Reprod.* **2**(Suppl.):11–17.
Dahl, H.-H. M., and D. R. Thorburn. 2001. Mitochondrial diseases: beyond the magic circle. *Am. J. Med. Genet.* **106**:1–3.
Daniell, H., M. S. Khan, and L. Allison. 2002. Milestones in chloroplast genetic engineering: an ... | {
"Header 1": "▲ FIGURE 10-12 Generation of retroviral genomic RNA from integrated retroviral DNA. The left LTR directs cellular RNA polymerase II to initiate transcription at the first nucleotide of the left R region. The resulting primary transcript extends beyond the right LTR. The right LTR, now present in the RN... |
Yeast RSC chromatin remodeling complex structure determined by electron microscopy. The complex (red) is shown bound to a nucleosome (yellow). [Courtesy of Francisco J. Asturias, 2002, *PNAS* 99:13477.]
n previous chapters we've seen that the actions and properties of each cell type ar... | {
"Header 1": "TRANSCRIPTIONAL CONTROL OF GENE EXPRESSION",
"token_count": 724,
"source_pdf": "datasets/websources/biochem/s-molecularcellbiology.pdf"
} |
In bacteria, gene control serves mainly to allow a single cell to adjust to changes in its environment so that its growth and division can be optimized. In multicellular organisms, environmental changes also induce changes in gene expression. An example is the response to low oxygen (hypoxia) that is described in Chapt... | {
"Header 1": "TRANSCRIPTIONAL CONTROL OF GENE EXPRESSION",
"Header 2": "11.1 Overview of Eukaryotic Gene Control and RNA Polymerases",
"token_count": 458,
"source_pdf": "datasets/websources/biochem/s-molecularcellbiology.pdf"
} |
Direct measurements of the transcription rates of multiple genes in different cell types have shown that regulation of transcription initiation is the most widespread form of gene control in eukaryotes, as it is in bacteria. *Nascent-chain analysis* is a common method for determining the relative rates of transcription... | {
"Header 1": "TRANSCRIPTIONAL CONTROL OF GENE EXPRESSION",
"Header 2": "Most Genes in Higher Eukaryotes Are Regulated by Controlling Their Transcription",
"token_count": 560,
"source_pdf": "datasets/websources/biochem/s-molecularcellbiology.pdf"
} |
In eukaryotes, as in bacteria, a DNA sequence that specifies where RNA polymerase binds and initiates transcription of a gene is called a **promoter.** Transcription from a particular promoter is controlled by DNA-binding proteins, termed transcription factors, that are equivalent to bacterial repressors and activators... | {
"Header 1": "TRANSCRIPTIONAL CONTROL OF GENE EXPRESSION",
"Header 2": "Regulatory Elements in Eukaryotic DNA Often Are Many Kilobases from Start Sites",
"token_count": 2025,
"source_pdf": "datasets/websources/biochem/s-molecularcellbiology.pdf"
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cerevisiae.* (a) The five subunits of the bacterial enzyme are distinguished by color. Only the N-terminal domains of the subunits are included in this model. (b) Ten of the twelve subunits constituting yeast RNA polymerase II are shown in this model.
Subunits that are similar in conformation to those in the bacteria... | {
"Header 1": "TRANSCRIPTIONAL CONTROL OF GENE EXPRESSION",
"Header 2": "Regulatory Elements in Eukaryotic DNA Often Are Many Kilobases from Start Sites",
"token_count": 1285,
"source_pdf": "datasets/websources/biochem/s-molecularcellbiology.pdf"
} |
Several experimental approaches have been used to identify DNA sequences at which RNA polymerase II initiates transcription. Approximate mapping of the transcription start
site is possible by exposing cultured cells or isolated nuclei to $^{32}\text{P-labeled}$ ribonucleotides for very brief times, as described ear... | {
"Header 1": "TRANSCRIPTIONAL CONTROL OF GENE EXPRESSION",
"Header 2": "RNA Polymerase II Initiates Transcription at DNA Sequences Corresponding to the 5' Cap of mRNAs",
"token_count": 2014,
"source_pdf": "datasets/websources/biochem/s-molecularcellbiology.pdf"
} |
Biol.* **212**:563, and http://www.epd.isb-sib.ck/promoter\_elements.]
where $A^{+1}$ is the base at which transcription starts, Y is a pyrimidine (C or T), N is any of the four bases, and T/A is T or A at position +3.
Transcription of genes with promoters containing a TATA box or initiator element begins at a we... | {
"Header 1": "TRANSCRIPTIONAL CONTROL OF GENE EXPRESSION",
"Header 2": "RNA Polymerase II Initiates Transcription at DNA Sequences Corresponding to the 5' Cap of mRNAs",
"token_count": 303,
"source_pdf": "datasets/websources/biochem/s-molecularcellbiology.pdf"
} |
Recombinant DNA techniques have been used to systematically mutate the nucleotide sequences upstream of the start sites of various eukaryotic genes in order to identify transcription-control regions. By now, hundreds of eukaryotic genes have been analyzed, and scores of transcription-control regions have been identifie... | {
"Header 1": "TRANSCRIPTIONAL CONTROL OF GENE EXPRESSION",
"Header 2": "Promoter-Proximal Elements Help Regulate Eukaryotic Genes",
"token_count": 2010,
"source_pdf": "datasets/websources/biochem/s-molecularcellbiology.pdf"
} |
For many genes, especially those encoding abundantly expressed proteins, a TATA box located approximately 25–35 base pairs upstream from the start site directs RNA polymerase II to begin transcription at the proper nucleotide. Promoter-proximal elements, which are relatively short (≈10–20 base pairs), are located withi... | {
"Header 1": "TRANSCRIPTIONAL CONTROL OF GENE EXPRESSION",
"Header 2": "Promoter-Proximal Elements Help Regulate Eukaryotic Genes",
"token_count": 2024,
"source_pdf": "datasets/websources/biochem/s-molecularcellbiology.pdf"
} |
Fractions containing protein that binds to the regulatory element in these assays probably contain a putative transcription factor. A powerful technique commonly used for the final step in purifying transcription factors is *sequencespecific DNA affinity chromatography,* a particular type of
**EXPERIMENTAL FIGURE 11-... | {
"Header 1": "TRANSCRIPTIONAL CONTROL OF GENE EXPRESSION",
"Header 2": "Promoter-Proximal Elements Help Regulate Eukaryotic Genes",
"token_count": 2000,
"source_pdf": "datasets/websources/biochem/s-molecularcellbiology.pdf"
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The structural model of eukaryotic activators that has emerged from these studies is a modular one in which one or more activation domains are connected to a sequence-specific DNA-binding domain through flexible protein domains (Figure 11-18). In some cases, amino acids included in the DNA-binding domain also contribut... | {
"Header 1": "TRANSCRIPTIONAL CONTROL OF GENE EXPRESSION",
"Header 2": "Promoter-Proximal Elements Help Regulate Eukaryotic Genes",
"token_count": 2033,
"source_pdf": "datasets/websources/biochem/s-molecularcellbiology.pdf"
} |
Many transcription factors contain multiple C2H2 zinc fingers, which interact with successive groups of base pairs, within the major groove, as the protein wraps around the DNA double helix (Figure 11-21a).
A second type of zinc-finger structure, designated the *C4 zinc finger* (because it has four conserved cysteine... | {
"Header 1": "TRANSCRIPTIONAL CONTROL OF GENE EXPRESSION",
"Header 2": "Promoter-Proximal Elements Help Regulate Eukaryotic Genes",
"token_count": 2020,
"source_pdf": "datasets/websources/biochem/s-molecularcellbiology.pdf"
} |
Each composite binding site is divided into two half-sites, and each heterodimeric factor contains the activation domains of its two constituent monomers. (b) Expression of an inhibitory factor (green) that interacts only with factor A inhibits binding; hence, transcriptional activation at sites 1, 4, and 5 is inhibite... | {
"Header 1": "TRANSCRIPTIONAL CONTROL OF GENE EXPRESSION",
"Header 2": "Promoter-Proximal Elements Help Regulate Eukaryotic Genes",
"token_count": 726,
"source_pdf": "datasets/websources/biochem/s-molecularcellbiology.pdf"
} |
Experiments with fusion proteins composed of the GAL4 DNA-binding domain and random segments of E. coli proteins demonstrated that a diverse group of amino acid sequences can function as activation domains, $\sim 1\%$ of all E. coli sequences, even though they evolved to perform other functions. Many transcription fa... | {
"Header 1": "TRANSCRIPTIONAL CONTROL OF GENE EXPRESSION",
"Header 2": "Structurally Diverse Activation and Repression Domains Regulate Transcription",
"token_count": 2023,
"source_pdf": "datasets/websources/biochem/s-molecularcellbiology.pdf"
} |
In general, these functional do-
mains interact with co-activators or co-repressors, which are critical to the ability of transcription factors to modulate gene expression.
■ Cooperative binding of multiple activators to nearby sites in an enhancer forms a multiprotein complex called an *enhancesome* (see Figure 11... | {
"Header 1": "TRANSCRIPTIONAL CONTROL OF GENE EXPRESSION",
"Header 2": "Structurally Diverse Activation and Repression Domains Regulate Transcription",
"token_count": 2034,
"source_pdf": "datasets/websources/biochem/s-molecularcellbiology.pdf"
} |
#### **KEY CONCEPTS OF SECTION 11.4**
#### **Transcription Initiation by RNA Polymerase II**
- Transcription of protein-coding genes by Pol II can be initiated in vitro by sequential binding of the following in the indicated order: TBP, which binds to TATA-box DNA; TFIIB; a complex of Pol II and TFIIF; TFIIE; and... | {
"Header 1": "TRANSCRIPTIONAL CONTROL OF GENE EXPRESSION",
"Header 2": "Structurally Diverse Activation and Repression Domains Regulate Transcription",
"token_count": 2024,
"source_pdf": "datasets/websources/biochem/s-molecularcellbiology.pdf"
} |
Several experiments using fluorescence confocal microscopy of yeast cells either stained with fluorescent-labeled antibody to any one of the SIR proteins or RAP1 or hybridized to a labeled telomere-specific DNA probe revealed that these proteins form large, condensed telomeric nucleoprotein structures resembling the he... | {
"Header 1": "TRANSCRIPTIONAL CONTROL OF GENE EXPRESSION",
"Header 2": "Structurally Diverse Activation and Repression Domains Regulate Transcription",
"token_count": 2035,
"source_pdf": "datasets/websources/biochem/s-molecularcellbiology.pdf"
} |
(b) Activatordirected hyperacetylation of histone N-terminal tails. The DNA-binding domain of the activator GCN4 interacts with specific upstream activating sequences (UAS) of the genes it regulates. The GCN4 activation domain (AD) then interacts with a multiprotein histone acetylase complex that includes the GCN5 cata... | {
"Header 1": "TRANSCRIPTIONAL CONTROL OF GENE EXPRESSION",
"Header 2": "Structurally Diverse Activation and Repression Domains Regulate Transcription",
"token_count": 2047,
"source_pdf": "datasets/websources/biochem/s-molecularcellbiology.pdf"
} |
[Courtesy of Andrew S. Belmont, 1999, *J. Cell Biol.* **145**:1341.]
higher-order chromatin structures. The net result of such chromatin remodeling is to facilitate the binding of transcription factors to DNA in chromatin. Some activation domains have been shown to bind to the SWI/SNF complex, and this binding stimul... | {
"Header 1": "TRANSCRIPTIONAL CONTROL OF GENE EXPRESSION",
"Header 2": "Structurally Diverse Activation and Repression Domains Regulate Transcription",
"token_count": 2039,
"source_pdf": "datasets/websources/biochem/s-molecularcellbiology.pdf"
} |
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