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In molecular biology, a downstream promoter element (DPE) is a core promoter element. Like all core promoters, the DPE plays an important role in the initiation of gene transcription by RNA polymerase II. The DPE was first described by T. W. Burke and James T. Kadonaga in Drosophila melanogaster at the University of California, San Diego in 1996. | https://en.wikipedia.org/wiki/Downstream_promoter_element |
It is also present in other species including humans, but not Saccharomyces cerevisiae.Together with the initiator motif (Inr), another core promoter element, the DPE is recognized by the transcription factor II D (TFIID) subunits TAF6 and TAF9. It has been shown that DPE-dependent basal transcription depends highly on the Inr (and vice versa) and on correct spacing between the two elements.The DPE consensus sequence was originally thought to be RGWCGTG, however more recent studies have suggested it to be the similar but more general sequence RGWYV(T). It is located about 28–33 nucleotides downstream of the transcription start site. | https://en.wikipedia.org/wiki/Downstream_promoter_element |
In molecular biology, a guanine tetrad (also known as a G-tetrad or G-quartet) is a structure composed of four guanine bases in a square planar array. They most prominently contribute to the structure of G-quadruplexes, where their hydrogen bonding stabilizes the structure. Usually, there are at least two guanine tetrads in a G-quadruplex, and they often feature Hoogsteen-style hydrogen bonding.Guanine tetrads are formed by sequences rich in guanine, such as GGGGC. | https://en.wikipedia.org/wiki/Guanine_tetrad |
They may also play a role in the dimerization of non-endogenous RNAs to facilitate the replication of some viruses. Guanine tetrads dimerize through their 5' ends since it is more energetically favorable.They can be stabilized by central cations, such as lithium, sodium, potassium, rubidium, or cesium. However, they still form a variety of different structures. | https://en.wikipedia.org/wiki/Guanine_tetrad |
Guanine tetrads are not always stable, but the sugar-phosphate backbone of DNA can assist in stability of the guanine tetrads themselves. Guanine tetrads are more stable when stacked, as intermolecular forces between each layers help stabilize them.Guanine tetrads can also influence recombination, replication, and transcription. For instance, guanine tetrads are found in the promoter region of the Myc family of oncogenes. They also function in immunoglobulin class switching and may play a role in the genome of HIV. Guanine tetrads appear frequently in the telomeric regions of DNA. | https://en.wikipedia.org/wiki/Guanine_tetrad |
In molecular biology, a histone octamer is the eight-protein complex found at the center of a nucleosome core particle. It consists of two copies of each of the four core histone proteins (H2A, H2B, H3, and H4). The octamer assembles when a tetramer, containing two copies of H3 and two of H4, complexes with two H2A/H2B dimers. Each histone has both an N-terminal tail and a C-terminal histone-fold. Each of these key components interacts with DNA in its own way through a series of weak interactions, including hydrogen bonds and salt bridges. These interactions keep the DNA and the histone octamer loosely associated, and ultimately allow the two to re-position or to separate entirely. | https://en.wikipedia.org/wiki/Histone_octamer |
In molecular biology, a hybridization probe (HP) is a fragment of DNA or RNA of usually 15–10000 nucleotide long which can be radioactively or fluorescently labeled. HP can be used to detect the presence of nucleotide sequences in analyzed RNA or DNA that are complementary to the sequence in the probe. The labeled probe is first denatured (by heating or under alkaline conditions such as exposure to sodium hydroxide) into single stranded DNA (ssDNA) and then hybridized to the target ssDNA (Southern blotting) or RNA (northern blotting) immobilized on a membrane or in situ. To detect hybridization of the probe to its target sequence, the probe is tagged (or "labeled") with a molecular marker of either radioactive or (more recently) fluorescent molecules. | https://en.wikipedia.org/wiki/Radioactive_probes |
Commonly used markers are 32P (a radioactive isotope of phosphorus incorporated into the phosphodiester bond in the probe DNA), digoxigenin, a non-radioactive, antibody-based marker, biotin or fluorescein. DNA sequences or RNA transcripts that have moderate to high sequence similarity to the probe are then detected by visualizing the hybridized probe via autoradiography or other imaging techniques. Normally, either X-ray pictures are taken of the filter, or the filter is placed under UV light. | https://en.wikipedia.org/wiki/Radioactive_probes |
Detection of sequences with moderate or high similarity depends on how stringent the hybridization conditions were applied—high stringency, such as high hybridization temperature and low salt in hybridization buffers, permits only hybridization between nucleic acid sequences that are highly similar, whereas low stringency, such as lower temperature and high salt, allows hybridization when the sequences are less similar. Hybridization probes used in DNA microarrays refer to DNA covalently attached to an inert surface, such as coated glass slides or gene chips, to which a mobile cDNA target is hybridized. Depending on the method, the probe may be synthesized using the phosphoramidite method, or it can be generated and labeled by PCR amplification or cloning (both are older methods). | https://en.wikipedia.org/wiki/Radioactive_probes |
In order to increase the in vivo stability of the probe RNA is not used. Instead, RNA analogues may be used, in particular morpholino- derivatives. Molecular DNA- or RNA-based probes are routinely used in screening gene libraries, detecting nucleotide sequences with blotting methods, and in other gene technologies, such as nucleic acid and tissue microarrays. | https://en.wikipedia.org/wiki/Radioactive_probes |
In molecular biology, a library is a collection of DNA fragments that is stored and propagated in a population of micro-organisms through the process of molecular cloning. There are different types of DNA libraries, including cDNA libraries (formed from reverse-transcribed RNA), genomic libraries (formed from genomic DNA) and randomized mutant libraries (formed by de novo gene synthesis where alternative nucleotides or codons are incorporated). DNA library technology is a mainstay of current molecular biology, genetic engineering, and protein engineering, and the applications of these libraries depend on the source of the original DNA fragments. There are differences in the cloning vectors and techniques used in library preparation, but in general each DNA fragment is uniquely inserted into a cloning vector and the pool of recombinant DNA molecules is then transferred into a population of bacteria (a Bacterial Artificial Chromosome or BAC library) or yeast such that each organism contains on average one construct (vector + insert). As the population of organisms is grown in culture, the DNA molecules contained within them are copied and propagated (thus, "cloned"). | https://en.wikipedia.org/wiki/Library_(biology) |
In molecular biology, a phage major coat protein is an alpha-helical protein that forms a viral envelope of filamentous bacteriophages. These bacteriophages are flexible rods, about one to two micrometres long and six nm in diameter, with a helical shell of protein subunits surrounding a DNA core. The approximately 50-residue subunit of the major coat protein is largely alpha-helix, and the axis of the alpha-helix makes a small angle with the axis of the virion. The protein shell can be considered in three sections: the outer surface, occupied by the N-terminal region of the subunit and rich in acidic residues that give the virion a low isoelectric point; the interior of the shell (including a 19-residue stretch of apolar side-chains) where protein subunits interact, mainly with each other; and the inner surface (occupied by the C-terminal region of the subunit), rich in positively charged residues that interact with the DNA core. == References == | https://en.wikipedia.org/wiki/Phage_major_coat_protein |
In molecular biology, a polynucleotide (from Ancient Greek πολυς (polys) 'many') is a biopolymer composed of 13 nucleotide monomers, covalently bonded in a chain. DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) are examples of polynucleotides with distinct biological functions. DNA consists of two chains of polynucleotides, with each chain in the form of a helix (like a spiral staircase). | https://en.wikipedia.org/wiki/Polynucleotide |
In molecular biology, a primosome is a protein complex responsible for creating RNA primers on single stranded DNA during DNA replication. The primosome consists of seven proteins: DnaG primase, DnaB helicase, DnaC helicase assistant, DnaT, PriA, Pri B, and PriC. At each replication fork, the primosome is utilized once on the leading strand of DNA and repeatedly, initiating each Okazaki fragment, on the lagging DNA strand. Initially the complex formed by PriA, PriB, and PriC binds to DNA. | https://en.wikipedia.org/wiki/Primosome |
Then the DnaB-DnaC helicase complex attaches along with DnaT. This structure is referred to as the pre-primosome. Finally, DnaG will bind to the pre-primosome forming a complete primosome. | https://en.wikipedia.org/wiki/Primosome |
The primosome attaches 1-10 RNA nucleotides to the single stranded DNA creating a DNA-RNA hybrid. This sequence of RNA is used as a primer to initiate DNA polymerase III. The RNA bases are ultimately replaced with DNA bases by RNase H nuclease (eukaryotes) or DNA polymerase I nuclease (prokaryotes). | https://en.wikipedia.org/wiki/Primosome |
DNA Ligase then acts to join the two ends together. Assembly of the Escherichia coli primosome requires six proteins, PriA, PriB, PriC, DnaB, DnaC, and DnaT, acting at a primosome assembly site (pas) on an SSBcoated single-stranded (8s) DNA. Assembly is initiated by interactions of PriA and PriB with ssDNA and the pas. | https://en.wikipedia.org/wiki/Primosome |
PriC, DnaB, DnaC, and DnaT then act on the PriAPriB- DNA complex to yield the primosome.Primosomes are nucleoproteins assemblies that activate DNA replication forks. Their primary role is to recruit the replicative helicase onto single-stranded DNA. The "replication restart" primosome, defined in Escherichia coli, is involved in the reactivation of arrested replication forks. | https://en.wikipedia.org/wiki/Primosome |
Binding of the PriA protein to forked DNA triggers its assembly. PriA is conserved in bacteria, but its primosomal partners are not. In Bacillus subtilis, genetic analysis has revealed three primosomal proteins, DnaB, DnaD, and DnaI, that have no obvious homologues in E. coli. | https://en.wikipedia.org/wiki/Primosome |
They are involved in primosome function both at arrested replication forks and at the chromosomal origin. Our biochemical analysis of the DnaB and DnaD proteins unravels their role in primosome assembly. They are both multimeric and bind individually to DNA. | https://en.wikipedia.org/wiki/Primosome |
Furthermore, DnaD stimulates DnaB binding activities. DnaD alone and the DnaD/DnaB pair interact specifically with PriA of B. subtilis on several DNA substrates. | https://en.wikipedia.org/wiki/Primosome |
This suggests that the nucleoprotein assembly is sequential in the PriA, DnaD, DnaB order. The preferred DNA substrate mimics an arrested DNA replication fork with unreplicated lagging strand, structurally identical to a product of recombinational repair of a stalled replication fork. == References == | https://en.wikipedia.org/wiki/Primosome |
In molecular biology, a protein domain is a region of a protein's polypeptide chain that is self-stabilizing and that folds independently from the rest. Each domain forms a compact folded three-dimensional structure. Many proteins consist of several domains, and a domain may appear in a variety of different proteins. | https://en.wikipedia.org/wiki/Protein_domain |
Molecular evolution uses domains as building blocks and these may be recombined in different arrangements to create proteins with different functions. In general, domains vary in length from between about 50 amino acids up to 250 amino acids in length. The shortest domains, such as zinc fingers, are stabilized by metal ions or disulfide bridges. Domains often form functional units, such as the calcium-binding EF hand domain of calmodulin. Because they are independently stable, domains can be "swapped" by genetic engineering between one protein and another to make chimeric proteins. | https://en.wikipedia.org/wiki/Protein_domain |
In molecular biology, a reading frame is a way of dividing the sequence of nucleotides in a nucleic acid (DNA or RNA) molecule into a set of consecutive, non-overlapping triplets. Where these triplets equate to amino acids or stop signals during translation, they are called codons. A single strand of a nucleic acid molecule has a phosphoryl end, called the 5′-end, and a hydroxyl or 3′-end. These define the 5′→3′ direction. | https://en.wikipedia.org/wiki/Reading_frame |
There are three reading frames that can be read in this 5′→3′ direction, each beginning from a different nucleotide in a triplet. In a double stranded nucleic acid, an additional three reading frames may be read from the other, complementary strand in the 5′→3′ direction along this strand. As the two strands of a double-stranded nucleic acid molecule are antiparallel, the 5′→3′ direction on the second strand corresponds to the 3′→5′ direction along the first strand.In general, at the most, one reading frame in a given section of a nucleic acid, is biologically relevant (open reading frame). Some viral transcripts can be translated using multiple, overlapping reading frames. There is one known example of overlapping reading frames in mammalian mitochondrial DNA: coding portions of genes for 2 subunits of ATPase overlap. | https://en.wikipedia.org/wiki/Reading_frame |
In molecular biology, a reporter gene (often simply reporter) is a gene that researchers attach to a regulatory sequence of another gene of interest in bacteria, cell culture, animals or plants. Such genes are called reporters because the characteristics they confer on organisms expressing them are easily identified and measured, or because they are selectable markers. Reporter genes are often used as an indication of whether a certain gene has been taken up by or expressed in the cell or organism population. | https://en.wikipedia.org/wiki/Reporter_gene |
In molecular biology, a scissile bond is a covalent chemical bond that can be broken by an enzyme. Examples would be the cleaved bond in the self-cleaving hammerhead ribozyme or the peptide bond of a substrate cleaved by a peptidase. == References == | https://en.wikipedia.org/wiki/Scissile_bond |
In molecular biology, a termination factor is a protein that mediates the termination of RNA transcription by recognizing a transcription terminator and causing the release of the newly made mRNA. This is part of the process that regulates the transcription of RNA to preserve gene expression integrity and are present in both eukaryotes and prokaryotes, although the process in bacteria is more widely understood. The most extensively studied and detailed transcriptional termination factor is the Rho (ρ) protein of E. coli. | https://en.wikipedia.org/wiki/Termination_factor |
In molecular biology, a transcription factor (TF) (or sequence-specific DNA-binding factor) is a protein that controls the rate of transcription of genetic information from DNA to messenger RNA, by binding to a specific DNA sequence. The function of TFs is to regulate—turn on and off—genes in order to make sure that they are expressed in the desired cells at the right time and in the right amount throughout the life of the cell and the organism. Groups of TFs function in a coordinated fashion to direct cell division, cell growth, and cell death throughout life; cell migration and organization (body plan) during embryonic development; and intermittently in response to signals from outside the cell, such as a hormone. There are 1500-1600 TFs in the human genome. | https://en.wikipedia.org/wiki/Transcription_factor |
Transcription factors are members of the proteome as well as regulome. TFs work alone or with other proteins in a complex, by promoting (as an activator), or blocking (as a repressor) the recruitment of RNA polymerase (the enzyme that performs the transcription of genetic information from DNA to RNA) to specific genes.A defining feature of TFs is that they contain at least one DNA-binding domain (DBD), which attaches to a specific sequence of DNA adjacent to the genes that they regulate. TFs are grouped into classes based on their DBDs. Other proteins such as coactivators, chromatin remodelers, histone acetyltransferases, histone deacetylases, kinases, and methylases are also essential to gene regulation, but lack DNA-binding domains, and therefore are not TFs.TFs are of interest in medicine because TF mutations can cause specific diseases, and medications can be potentially targeted toward them. | https://en.wikipedia.org/wiki/Transcription_factor |
In molecular biology, a twintron is an intron-within-intron excised by sequential splicing reactions. A twintron is presumably formed by the insertion of a mobile intron into an existing intron. | https://en.wikipedia.org/wiki/Twintron |
In molecular biology, acetate kinase (EC 2.7.2.1), which is predominantly found in micro-organisms, facilitates the production of acetyl-CoA by phosphorylating acetate in the presence of ATP and a divalent cation. Short-chain fatty acids (SCFAs) play a major role in carbon cycle and can be utilized as a source of carbon and energy by bacteria. Salmonella typhimurium propionate kinase (StTdcD) catalyzes reversible transfer of the γ-phosphate of ATP to propionate during l-threonine degradation to propionate. Kinetic analysis revealed that StTdcD possesses broad ligand specificity and could be activated by various SCFAs (propionate>acetate≈butyrate), nucleotides (ATP≈GTP>CTP≈TTP; dATP>dGTP>dCTP) and metal ions (Mg2+≈Mn2+>Co2+). | https://en.wikipedia.org/wiki/Acetate_kinase |
Inhibition of StTdcD by tricarboxylic acid (TCA) cycle intermediates such as citrate, succinate, α-ketoglutarate and malate suggests that the enzyme could be under plausible feedback regulation. Crystal structures of StTdcD bound to PO4 (phosphate), AMP, ATP, Ap4 (adenosine tetraphosphate), GMP, GDP, GTP, CMP and CTP revealed that binding of nucleotide mainly involves hydrophobic interactions with the base moiety and could account for the broad biochemical specificity observed between the enzyme and nucleotides. Modelling and site-directed mutagenesis studies suggest Ala88 to be an important residue involved in determining the rate of catalysis with SCFA substrates. | https://en.wikipedia.org/wiki/Acetate_kinase |
Molecular dynamics simulations on monomeric and dimeric forms of StTdcD revealed plausible open and closed states, and also suggested role for dimerization in stabilizing segment 235-290 involved in interfacial interactions and ligand binding. Observation of an ethylene glycol molecule bound sufficiently close to the γ-phosphate in StTdcD complexes with triphosphate nucleotides supports direct in-line phosphoryl transfer. The enzyme is important in the process of glycolysis, enzyme levels being increased in the presence of excess glucose. | https://en.wikipedia.org/wiki/Acetate_kinase |
The growth of a bacterial mutant lacking acetate kinase has been shown to be inhibited by glucose, suggesting that the enzyme is involved in excretion of excess carbohydrate. A related enzyme, butyrate kinase, facilitates the formation of butyryl-CoA by phosphorylating butyrate in the presence of ATP to form butyryl phosphate. == References == | https://en.wikipedia.org/wiki/Acetate_kinase |
In molecular biology, adenylosuccinate synthase (or adenylosuccinate synthetase) (EC 6.3.4.4) is an enzyme that plays an important role in purine biosynthesis, by catalysing the guanosine triphosphate (GTP)-dependent conversion of inosine monophosphate (IMP) and aspartic acid to guanosine diphosphate (GDP), phosphate and N(6)-(1,2-dicarboxyethyl)-AMP. Adenylosuccinate synthetase has been characterised from various sources ranging from Escherichia coli (gene purA) to vertebrate tissues. In vertebrates, two isozymes are present: one involved in purine biosynthesis and the other in the purine nucleotide cycle. | https://en.wikipedia.org/wiki/Adenylosuccinate_synthetase |
In molecular biology, aerolysin is a cytolytic pore-forming toxin exported by Aeromonas hydrophila, a Gram-negative bacterium associated with diarrhoeal diseases and deep wound infections. The mature toxin binds to eukaryotic cells and aggregates to form holes (approximately 3 nm in diameter) leading to the destruction of the membrane permeability barrier and osmotic lysis. The structure of proaerolysin has been determined to 2.8A resolution and shows the protoxin to adopt a novel fold. Images of an aerolysin oligomer derived from electron microscopy have helped to construct a model of the protein in its heptameric conformation, and to outline a mechanism by which this assembly might insert into lipid bilayers to form ion channels. == References == | https://en.wikipedia.org/wiki/Aerolysin |
In molecular biology, alanine scanning is a site-directed mutagenesis technique used to determine the contribution of a specific residue to the stability or function of a given protein. Alanine is used because of its non-bulky, chemically inert, methyl functional group that nevertheless mimics the secondary structure preferences that many of the other amino acids possess. Sometimes bulky amino acids such as valine or leucine are used in cases where conservation of the size of mutated residues is needed. This technique can also be used to determine whether the side chain of a specific residue plays a significant role in bioactivity. | https://en.wikipedia.org/wiki/Alanine_scanning |
This is usually accomplished by site-directed mutagenesis or randomly by creating a PCR library. Furthermore, computational methods to estimate thermodynamic parameters based on theoretical alanine substitutions have been developed. This technique is rapid, because many side chains are analyzed simultaneously and the need for protein purification and biophysical analysis is circumvented. | https://en.wikipedia.org/wiki/Alanine_scanning |
The technology is very mature at this point and is widely used in biochemical fields. The data can be tested by IR, NMR Spectroscopy, mathematical methods, bioassays, etc.One good example of alanine scanning is the examination of the role of charged residues on the surface of proteins. In a systematic study on the roles of conserved charged residues on the surface of epithelial sodium channel (ENaC), alanine scanning was used to reveal the importance of charged residues for the process of transport of the proteins to the cell surface. | https://en.wikipedia.org/wiki/Alanine_scanning |
In molecular biology, alpha-amylase inhibitor (or α-...) is a protein family which inhibits mammalian alpha-amylases specifically, by forming a tight stoichiometric 1:1 complex with alpha-amylase. This family of inhibitors has no action on plant and microbial alpha amylases. A crystal structure has been determined for tendamistat, the 74-amino acid inhibitor produced by Streptomyces tendae that targets a wide range of mammalian alpha-amylases. The binding of tendamistat to alpha-amylase leads to the steric blockage of the active site of the enzyme. | https://en.wikipedia.org/wiki/Alpha_amylase_inhibitor |
The crystal structure of tendamistat revealed an immunoglobulin-like fold that could potentially adopt multiple conformations. Such molecular flexibility could enable an induced-fit type of binding that would both optimise binding and allow broad target specificity. == References == | https://en.wikipedia.org/wiki/Alpha_amylase_inhibitor |
In molecular biology, an Anfinsen cage is a model for protein folding used by some cells to improve the production speed and yield of accurate products. Space within a cell is generally limited, and a protein's folding process can be interrupted or modified if it wanders too close to outside forces while it is still in the process of forming. Even worse, the unformed molecules may begin to aggregate uncontrollably, potentially resulting in a disease such as Alzheimer's.To prevent this, some cells will enclose actively folding proteins within one or more chaperones, forming a "cage" around them to protect them during their transformation. | https://en.wikipedia.org/wiki/Anfinsen_cage |
These cages can also serve to isolate incorrectly formed proteins that may otherwise affect other processes if it were allowed to float freely. The model is named after Christian B. Anfinsen who first showed in vitro that pure denatured proteins will sometimes refold spontaneously without an energy source. == References == | https://en.wikipedia.org/wiki/Anfinsen_cage |
In molecular biology, an actomyosin contractile ring is a prominent structure during cytokinesis. It forms perpendicular to the axis of the spindle apparatus towards the end of telophase, in which sister chromatids are identically separated at the opposite sides of the spindle forming nuclei (Figure 1). The actomyosin ring follows an orderly sequence of events: identification of the active division site, formation of the ring, constriction of the ring, and disassembly of the ring. It is composed of actin and myosin II bundles, thus the term actomyosin. | https://en.wikipedia.org/wiki/Actomyosin_ring |
The actomyosin ring operates in contractile motion, although the mechanism on how or what triggers the constriction is still an evolving topic. Other cytoskeletal proteins are also involved in maintaining the stability of the ring and driving its constriction. Apart from cytokinesis, in which the ring constricts as the cells divide (Figure 2), actomyosin ring constriction has also been found to activate during wound closure. | https://en.wikipedia.org/wiki/Actomyosin_ring |
During this process, actin filaments are degraded, preserving the thickness of the ring. After cytokinesis is complete, one of the two daughter cells inherits a remnant known as the midbody ring.Activation of the cell-cycle kinase (e.g. Rho-kinases) during telophase initiates constriction of the actomyosin ring by creating a groove that migrates in an inward motion. Rho-kinases such as ROCK1 has been found to regulate actomyosin contraction through phosphorylation of the myosin light chain (MLC). This mechanism promotes cell-cell contacts and integrity leading to adhesion formation. | https://en.wikipedia.org/wiki/Actomyosin_ring |
In molecular biology, an amplicon is a piece of DNA or RNA that is the source and/or product of amplification or replication events. It can be formed artificially, using various methods including polymerase chain reactions (PCR) or ligase chain reactions (LCR), or naturally through gene duplication. In this context, amplification refers to the production of one or more copies of a genetic fragment or target sequence, specifically the amplicon. | https://en.wikipedia.org/wiki/Amplicon_sequencing |
As it refers to the product of an amplification reaction, amplicon is used interchangeably with common laboratory terms, such as "PCR product." Artificial amplification is used in research, forensics, and medicine for purposes that include detection and quantification of infectious agents, identification of human remains, and extracting genotypes from human hair.Natural gene duplication plays a major role in evolution. It is also implicated in several forms of human cancer including primary mediastinal B cell lymphoma and Hodgkin's lymphoma. In this context the term amplicon can refer both to a section of chromosomal DNA that has been excised, amplified, and reinserted elsewhere in the genome, and to a fragment of extrachromosomal DNA known as a double minute, each of which can be composed of one or more genes. Amplification of the genes encoded by these amplicons generally increases transcription of those genes and ultimately the volume of associated proteins. | https://en.wikipedia.org/wiki/Amplicon_sequencing |
In molecular biology, an annexin A5 affinity assay is a test to quantify the number of cells undergoing apoptosis. The assay uses the protein annexin A5 to tag apoptotic and dead cells, and the numbers are then counted using either flow cytometry or a fluorescence microscope.The annexin a5 protein binds to apoptotic cells in a calcium-dependent manner using phosphatidylserine-containing membrane surfaces that are usually present only on the inner leaflet of the membrane. | https://en.wikipedia.org/wiki/Annexin_A5_affinity_assay |
In molecular biology, an arginine finger is an amino acid residue of some enzymes. Arginine fingers are often found in the protein superfamily of AAA+ ATPases, GTPases, and dUTPases, where they assist in the catalysis of the gamma phosphate or gamma and beta phosphates from ATP or GTP, which creates a release of energy which can be used to perform cellular work. They are also found in GTPase-activating proteins (GAP). Thus, they are essential for many forms of life, and are highly conserved. Arginine fingers function through non-covalent interactions. They may also assist in dimerization, and while they are found in a wide variety of enzymes, they are not ubiquitous. | https://en.wikipedia.org/wiki/Arginine_finger |
In molecular biology, an autotransporter domain is a structural domain found in some bacterial outer membrane proteins. The domain is always located at the C-terminal end of the protein and forms a beta-barrel structure. The barrel is oriented in the membrane such that the N-terminal portion of the protein, termed the passenger domain, is presented on the cell surface. | https://en.wikipedia.org/wiki/Autotransporter_family |
These proteins are typically virulence factors, associated with infection or virulence in pathogenic bacteria. The name autotransporter derives from an initial understanding that the protein was self-sufficient in transporting the passenger domain through the outermembrane. This view has since been challenged by Benz and Schmidt.Secretion of polypeptide chains through the outer membrane of Gram-negative bacteria can occur via a number of different pathways. | https://en.wikipedia.org/wiki/Autotransporter_family |
The type V(a), or autotransporter, secretion pathway constitutes the largest number of secreted virulence factors of any one of the seven known types of secretion in Gram-negative bacteria. This secretion pathway is exemplified by the prototypical IgA1 Protease of Neisseria gonorrhoeae. The protein is directed to the inner membrane by a signal peptide transported across the inner membrane via the Sec machinery. | https://en.wikipedia.org/wiki/Autotransporter_family |
Once in the periplasm, the autotransporter domain inserts into the outer membrane. The passenger domain is passed through the center of the autotransporter domain to be presented on the outside of the cell, however the mechanism by which this occurs remains unclear.The C-terminal translocator domain corresponds to an outer membrane beta-barrel domain. The N-terminal passenger domain is translocated across the membrane, and may or may not be cleaved from the translocator domain. | https://en.wikipedia.org/wiki/Autotransporter_family |
In those proteins where the cleavage is auto-catalytic, the peptidase domains belong to MEROPS peptidase families S6 and S8. Passenger domains structurally characterized to date have been shown to be dominated by a protein fold known as a beta helix, typified by pertactin. The folding of this domain is thought to be intrinsically linked to its method of outer membrane translocation. | https://en.wikipedia.org/wiki/Autotransporter_family |
In molecular biology, an exonic splicing enhancer (ESE) is a DNA sequence motif consisting of 6 bases within an exon that directs, or enhances, accurate splicing of heterogeneous nuclear RNA (hnRNA) or pre-mRNA into messenger RNA (mRNA). | https://en.wikipedia.org/wiki/Exonic_splicing_enhancers |
In molecular biology, an inducer is a molecule that regulates gene expression. An inducer functions in two ways; namely: By disabling repressors. The gene is expressed because an inducer binds to the repressor. The binding of the inducer to the repressor prevents the repressor from binding to the operator. | https://en.wikipedia.org/wiki/Inducer |
RNA polymerase can then begin to transcribe operon genes. By binding to activators. | https://en.wikipedia.org/wiki/Inducer |
Activators generally bind poorly to activator DNA sequences unless an inducer is present. Activator binds to an inducer and the complex binds to the activation sequence and activates target gene. Removing the inducer stops transcription.Because a small inducer molecule is required, the increased expression of the target gene is called induction. The lactose operon is one example of an inducible system. | https://en.wikipedia.org/wiki/Inducer |
In molecular biology, an interactome is the whole set of molecular interactions in a particular cell. The term specifically refers to physical interactions among molecules (such as those among proteins, also known as protein–protein interactions, PPIs; or between small molecules and proteins) but can also describe sets of indirect interactions among genes (genetic interactions). The word "interactome" was originally coined in 1999 by a group of French scientists headed by Bernard Jacq. Mathematically, interactomes are generally displayed as graphs. Though interactomes may be described as biological networks, they should not be confused with other networks such as neural networks or food webs. | https://en.wikipedia.org/wiki/Interactome |
In molecular biology, an intrinsically disordered protein (IDP) is a protein that lacks a fixed or ordered three-dimensional structure, typically in the absence of its macromolecular interaction partners, such as other proteins or RNA. IDPs range from fully unstructured to partially structured and include random coil, molten globule-like aggregates, or flexible linkers in large multi-domain proteins. They are sometimes considered as a separate class of proteins along with globular, fibrous and membrane proteins.IDPs are a very large and functionally important class of proteins and their discovery has disproved the idea that three-dimensional structures of proteins must be fixed to accomplish their biological functions. For example, IDPs have been identified to participate in weak multivalent interactions that are highly cooperative and dynamic, lending them importance in DNA regulation and in cell signaling. Many IDPs can also adopt a fixed three-dimensional structure after binding to other macromolecules. Overall, IDPs are different from structured proteins in many ways and tend to have distinctive function, structure, sequence, interactions, evolution and regulation. | https://en.wikipedia.org/wiki/Intrinsically_disordered_proteins |
In molecular biology, an oscillating gene is a gene that is expressed in a rhythmic pattern or in periodic cycles. Oscillating genes are usually circadian and can be identified by periodic changes in the state of an organism. Circadian rhythms, controlled by oscillating genes, have a period of approximately 24 hours. For example, plant leaves opening and closing at different times of the day or the sleep-wake schedule of animals can all include circadian rhythms. | https://en.wikipedia.org/wiki/Gene_oscillations |
Other periods are also possible, such as 29.5 days resulting from circalunar rhythms or 12.4 hours resulting from circatidal rhythms. Oscillating genes include both core clock component genes and output genes. A core clock component gene is a gene necessary for to the pacemaker. However, an output oscillating gene, such as the AVP gene, is rhythmic but not necessary to the pacemaker. | https://en.wikipedia.org/wiki/Gene_oscillations |
In molecular biology, and more importantly high-throughput DNA sequencing, a chimera is a single DNA sequence originating when multiple transcripts or DNA sequences get joined. Chimeras can be considered artifacts and be filtered out from the data during processing to prevent spurious inferences of biological variation. However, chimeras should not be confused with chimeric reads, who are generally used by structural variant callers to detect structural variation events and are not always an indication of the presence of a chimeric transcript or gene. | https://en.wikipedia.org/wiki/Chimera_(molecular_biology) |
In a different context, the deliberate creation of artificial chimeras can also be a useful tool in molecular biology. For example, in protein engineering, "chimeragenesis" (forming chimeras between proteins that are encoded by homologous cDNAs) is one of the "two major techniques used to manipulate cDNA sequences". For gene fusions that occur through natural processes, see chimeric genes and fusion genes. | https://en.wikipedia.org/wiki/Chimera_(molecular_biology) |
In molecular biology, apical membrane antigen 1 is a novel antigen of Plasmodium falciparum which has been cloned. It contains a hydrophobic domain typical of an integral membrane protein. The antigen is designated apical membrane antigen 1 (AMA-1) by virtue of appearing to be located in the apical complex. AMA-1 appears to be transported to the merozoite surface close to the time of schizont rupture. | https://en.wikipedia.org/wiki/Apical_membrane_antigen_1 |
The 66kDa merozoite surface antigen (PK66) of Plasmodium knowlesi, a simian malaria, possesses vaccine-related properties believed to originate from a receptor-like role in parasite invasion of erythrocytes. The sequence of PK66 is conserved throughout Plasmodium, and shows high similarity to P. falciparum AMA-1. Following schizont rupture, the distribution of PK66 changes in a coordinate manner associated with merozoite invasion. | https://en.wikipedia.org/wiki/Apical_membrane_antigen_1 |
Prior to rupture, the protein is concentrated at the apical end, following which it distributes itself entirely across the surface of the free merozoite. Immunofluorescence studies suggest that, during invasion, PK66 is excluded from the erythrocyte at, and behind, the invasion interface. == References == | https://en.wikipedia.org/wiki/Apical_membrane_antigen_1 |
In molecular biology, apovitellenin-1 is a family of proteins found in birds. As part of the avian reproductive effort, large quantities of triglyceride-rich very-low-density lipoprotein (VLDL) particles are transported by receptor-mediated endocytosis into the female germ cells, apovitellenin-1 is a protein component of this VLDL. Although the oocytes are surrounded by a layer of granulosa cells harbouring high levels of active lipoprotein lipase, non-lipolysed VLDL is transported into the yolk. | https://en.wikipedia.org/wiki/Apovitellenin-1 |
This is because the VLDL particles are protected from lipolysis by apovitellenin-1a, which acts as a potent dimeric lipoprotein lipase inhibitor. Apo-VLDL-II is produced in the liver and secreted into the blood stream when induced by estrogen production in female birds. == References == | https://en.wikipedia.org/wiki/Apovitellenin-1 |
In molecular biology, autophagy related 3 (Atg3) is the E2 enzyme for the LC3 lipidation process. It is essential for autophagy. The super protein complex, the Atg16L complex, consists of multiple Atg12-Atg5 conjugates. | https://en.wikipedia.org/wiki/ATG3 |
Atg16L has an E3-like role in the LC3 lipidation reaction. The activated intermediate, LC3-Atg3 (E2), is recruited to the site where the lipidation takes place.Atg3 catalyses the conjugation of Atg8 and phosphatidylethanolamine (PE). Atg3 has an alpha/beta-fold, and its core region is topologically similar to canonical E2 enzymes. | https://en.wikipedia.org/wiki/ATG3 |
Atg3 has two regions inserted in the core region and another with a long alpha-helical structure that protrudes from the core region as far as 30 A. It interacts with atg8 through an intermediate thioester bond between Cys-288 and the C-terminal Gly of atg8. It also interacts with the C-terminal region of the E1-like atg7 enzyme. Autophagocytosis is a starvation-induced process responsible for transport of cytoplasmic proteins to the lysosome/vacuole. | https://en.wikipedia.org/wiki/ATG3 |
Atg3 is a ubiquitin like modifier that is topologically similar to the canonical E2 enzyme. It catalyses the conjugation of Atg8 and phosphatidylethanolamine.Atg3 consists of three domains, an N-terminal domain, a catalytic domain and a C-terminal domain. The catalytic domain contains a cysteine residue within an HPC motif, this is the putative active-site residue for recognition of the Apg5 subunit of the autophagosome complex. | https://en.wikipedia.org/wiki/ATG3 |
The small C-terminal domain is likely to be a distinct binding region for the stability of the autophagosome complex. It carries a highly characteristic conserved FLKF sequence motif. == References == | https://en.wikipedia.org/wiki/ATG3 |
In molecular biology, autotransporter proteins are proteins secreted out the Gram-negative bacteria. These beta helixes require a domain which is called the intramolecular autochaperone domain. It shows similarities with other intramolecular chaperone sequences and has a folding-associated function. This increases the efficiency, either by stabilizing the beta-barrel, or by promoting the folding of the passenger domain. | https://en.wikipedia.org/wiki/Autochaperone |
The autochaperone domain is usually located between the HSF and the passenger domain. When the passenger domain is translocated, starting with its C terminus, the autochaperone domain is first out. This would result in the formation of a hairpin structure. | https://en.wikipedia.org/wiki/Autochaperone |
In molecular biology, bacterial DNA binding proteins are a family of small, usually basic proteins of about 90 residues that bind DNA and are known as histone-like proteins. Since bacterial binding proteins have a diversity of functions, it has been difficult to develop a common function for all of them. They are commonly referred to as histone-like and have many similar traits with the eukaryotic histone proteins. | https://en.wikipedia.org/wiki/Bacterial_DNA_binding_protein |
Eukaryotic histones package DNA to help it to fit in the nucleus, and they are known to be the most conserved proteins in nature. Examples include the HU protein in Escherichia coli, a dimer of closely related alpha and beta chains and in other bacteria can be a dimer of identical chains. HU-type proteins have been found in a variety of bacteria (including cyanobacteria) and archaea, and are also encoded in the chloroplast genome of some algae. The integration host factor (IHF), a dimer of closely related chains which is suggested to function in genetic recombination as well as in translational and transcriptional control is found in Enterobacteria and viral proteins including the African swine fever virus protein A104R (or LMW5-AR).This family is also found in a group of eukaryotes known as dinoflagellates. These dinoflagellate histone-like proteins replace histone in some dinoflagellates and package DNA into a liquid-crystalline state. | https://en.wikipedia.org/wiki/Bacterial_DNA_binding_protein |
In molecular biology, bacteriophage scaffolding proteins are proteins involved in bacteriophage assembly. The assembly of a macromolecular structure proceeds via a specific pathway of ordered events and involves conformational changes in the proteins as they join the assembly. The assembly process is aided by scaffolding proteins, which act as chaperones. In bacteriophage, scaffolding proteins B and D are responsible for procapsid formation. | https://en.wikipedia.org/wiki/Bacteriophage_scaffolding_proteins |
240 copies of protein D form the external scaffold, while 60 copies of protein B form the internal scaffold. The role of scaffolding protein D is in the production of viral single-stranded RNA. == References == | https://en.wikipedia.org/wiki/Bacteriophage_scaffolding_proteins |
In molecular biology, barrier-to-autointegration factor (BAF) is a family of essential proteins that is highly conserved in metazoan evolution, and which may act as DNA-bridging proteins. BAF binds directly to double-stranded DNA, to transcription activators, and to inner nuclear membrane proteins, including lamin A filaments that anchor nuclear pore complexes in place, and nuclear LEM-domain proteins that bind to lamin filaments and chromatin. New findings suggest that BAF has structural roles in nuclear assembly and chromatin organization, represses gene expression and might interlink chromatin structure, nuclear architecture and gene regulation in metazoans.BAF can be exploited by retroviruses to act as a host component of pre-integration complexes, which promote the integration of the retroviral DNA into the host chromosome by preventing autointegration (integration into itself). BAF might contribute to the assembly or activity of retroviral pre-integration complexes through direct binding to the retroviral proteins p55 Gag and matrix, as well as to DNA. == References == | https://en.wikipedia.org/wiki/Barrier-to-autointegration_factor |
In molecular biology, binding domain is a protein domain which binds to a specific atom or molecule, such as calcium or DNA. A protein domain is a part of a protein sequence and a tertiary structure that can change or evolve, function, and live by itself independent of the rest of the protein chain. Upon binding, proteins may undergo a conformational change. Binding domains are essential for the function of many proteins. They are essential because they help splice, assemble, and translate proteins.Examples of binding domains include the Zinc finger, which binds to DNA, and EF hand, which binds to calcium. | https://en.wikipedia.org/wiki/Binding_domain |
In molecular biology, biochips are engineered substrates ("miniaturized laboratories") that can host large numbers of simultaneous biochemical reactions. One of the goals of biochip technology is to efficiently screen large numbers of biological analytes, with potential applications ranging from disease diagnosis to detection of bioterrorism agents. For example, digital microfluidic biochips are under investigation for applications in biomedical fields. In a digital microfluidic biochip, a group of (adjacent) cells in the microfluidic array can be configured to work as storage, functional operations, as well as for transporting fluid droplets dynamically. | https://en.wikipedia.org/wiki/Biochip |
In molecular biology, biosynthesis is a multi-step, enzyme-catalyzed process where substrates are converted into more complex products in living organisms. In biosynthesis, simple compounds are modified, converted into other compounds, or joined to form macromolecules. This process often consists of metabolic pathways. | https://en.wikipedia.org/wiki/Biological_synthesis |
Some of these biosynthetic pathways are located within a single cellular organelle, while others involve enzymes that are located within multiple cellular organelles. Examples of these biosynthetic pathways include the production of lipid membrane components and nucleotides. Biosynthesis is usually synonymous with anabolism. | https://en.wikipedia.org/wiki/Biological_synthesis |
The prerequisite elements for biosynthesis include: precursor compounds, chemical energy (e.g. ATP), and catalytic enzymes which may need coenzymes (e.g. NADH, NADPH). These elements create monomers, the building blocks for macromolecules. Some important biological macromolecules include: proteins, which are composed of amino acid monomers joined via peptide bonds, and DNA molecules, which are composed of nucleotides joined via phosphodiester bonds. | https://en.wikipedia.org/wiki/Biological_synthesis |
In molecular biology, calmodulin binding domain (CaMBD) is a protein domain found in small-conductance calcium-activated potassium channels (SK channels). These channels are independent of voltage and gated solely by intracellular Ca2+. They are heteromeric complexes that comprise pore-forming alpha-subunits and the Ca2+-binding protein calmodulin (CaM). CaM binds to the SK channel through the CaMBD, which is located in an intracellular region of the alpha-subunit immediately carboxy-terminal to the pore. | https://en.wikipedia.org/wiki/Calmodulin_binding_domain |
Channel opening is triggered when Ca2+ binds the EF hands in the N-lobe of CaM. The structure of this domain complexed with CaM is known. This domain forms an elongated dimer with a CaM molecule bound at each end; each CaM wraps around three alpha-helices, two from one CaMBD subunit and one from the other. == References == | https://en.wikipedia.org/wiki/Calmodulin_binding_domain |
In molecular biology, cia-dependent small RNAs (csRNAs) are small RNAs produced by Streptococci. These RNAs are part of the regulon of the CiaRH two-component regulatory system. Two of these RNAs, csRNA4 and csRNA5, have been shown to affect stationary-phase autolysis. | https://en.wikipedia.org/wiki/Cia-dependent_small_RNAs |
In molecular biology, cob(I)yrinic acid a,c-diamide adenosyltransferase (also known as ATP:cob(I)alamin adenosyltransferase or ATP:corrinoid adenosyltransferase) EC 2.5.1.17 is an enzyme which catalyses the conversion of cobalamin (vitamin B12) into one of its coenzyme forms, adenosylcobalamin (coenzyme B12, AdoCbl). Adenosylcobalamin is required as a cofactor for the activity of certain enzymes. AdoCbl contains an adenosyl moiety liganded to the cobalt ion of cobalamin via a covalent Co-C bond. ATP:cob(I)alamin adenosyltransferases are classed into three groups: CobA-type, EutT-type and PduO-type. | https://en.wikipedia.org/wiki/Cob(I)yrinic_acid_a,c-diamide_adenosyltransferase |
Each of the three enzyme types appears to be specialised for particular AdoCbl-dependent enzymes or for the de novo synthesis of AdoCbl. PduO and EutT are distantly related, sharing short conserved motifs, while CobA is evolutionarily unrelated and is an example of convergent evolution. The CobA group includes the ATP:cob(I)alamin adenosyltransferases CobA (Salmonella typhimurium), CobO (Pseudomonas denitrificans), and ButR (Escherichia coli). | https://en.wikipedia.org/wiki/Cob(I)yrinic_acid_a,c-diamide_adenosyltransferase |
There is a high degree of sequence identity between these proteins. CobA is responsible for attaching the adenosyl moiety from ATP to the cobalt ion of the corrin ring, necessary for the conversion of cobalamin to adenosylcobalamin. PduO functions to convert cobalamin to AdoCbl for 1,2-propanediol degradation, while EutT produces AdoCbl for ethanolamine utilisation. | https://en.wikipedia.org/wiki/Cob(I)yrinic_acid_a,c-diamide_adenosyltransferase |
In molecular biology, communication between neurons typically occurs by chemical transmission across gaps between the cells called synapses. The transmitted chemicals, known as neurotransmitters, regulate a significant fraction of vital body functions. It is possible to anatomically locate neurotransmitters by labeling techniques. It is possible to chemically identify certain neurotransmitters such as catecholamines by fixing neural tissue sections with formaldehyde. | https://en.wikipedia.org/wiki/Molecular_Neuroscience |
This can give rise to formaldehyde-induced fluorescence when exposed to ultraviolet light. Dopamine, a catecholamine, was identified in the nematode C. elegans by using this technique.Immunocytochemistry, which involves raising antibodies against targeted chemical or biological entities, includes a few other techniques of interest. A targeted neurotransmitter could be specifically tagged by primary and secondary antibodies with radioactive labeling in order to identify the neurotransmitter by autoradiography. The presence of neurotransmitters (though not necessarily the location) can be observed in enzyme-linked immunocytochemistry or enzyme-linked immunosorbent assays (ELISA) in which substrate-binding in the enzymatic assays can induce precipitates, fluorophores, or chemiluminescence. In the event that neurotransmitters cannot be histochemically identified, an alternative method is to locate them by their neural uptake mechanisms. | https://en.wikipedia.org/wiki/Molecular_Neuroscience |
In molecular biology, complementarity describes a relationship between two structures each following the lock-and-key principle. In nature complementarity is the base principle of DNA replication and transcription as it is a property shared between two DNA or RNA sequences, such that when they are aligned antiparallel to each other, the nucleotide bases at each position in the sequences will be complementary, much like looking in the mirror and seeing the reverse of things. This complementary base pairing allows cells to copy information from one generation to another and even find and repair damage to the information stored in the sequences. The degree of complementarity between two nucleic acid strands may vary, from complete complementarity (each nucleotide is across from its opposite) to no complementarity (each nucleotide is not across from its opposite) and determines the stability of the sequences to be together. | https://en.wikipedia.org/wiki/Complementary_base_sequence |
Furthermore, various DNA repair functions as well as regulatory functions are based on base pair complementarity. In biotechnology, the principle of base pair complementarity allows the generation of DNA hybrids between RNA and DNA, and opens the door to modern tools such as cDNA libraries. While most complementarity is seen between two separate strings of DNA or RNA, it is also possible for a sequence to have internal complementarity resulting in the sequence binding to itself in a folded configuration. | https://en.wikipedia.org/wiki/Complementary_base_sequence |
In molecular biology, copines is a name for the group of human proteins that includes members such as CPNE1, CPNE4, CPNE6, and CPNE8. These are highly conserved, calcium-dependent membrane proteins found in a variety of eukaryotes. The domain structure of these 55 kDa proteins suggests that they may have a role in membrane trafficking in some prokaryotes as well as eukaryotes. Copines contains two C2 domains which play a role in signal transduction by binding to calcium, phospholipids, or polyphosphates. | https://en.wikipedia.org/wiki/Copine |
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