---
license: mit
language:
- en
library_name: pytorch
tags:
- biology
- proteins
- peptides
- binding-site-prediction
- esm3
- kan
- protein-language-model
- drug-design
pipeline_tag: token-classification
---

# GeoPep

**Geometric-aware Peptide-Protein Binding Site Prediction**

GeoPep is a per-residue binding site predictor that combines the ESM3 protein
foundation model with Kolmogorov-Arnold Network (KAN) heads. Given a peptide
and a protein, it predicts which residues of the protein bind the peptide and
which residues of the peptide make contact.

- 📦 Code: https://github.com/Dian0212/GeoPep
- 📄 Checkpoint: `model_distanceLoss.ckpt` (~16 GB)

## Model Summary

| | |
|---|---|
| **Backbone** | ESM3 (sm-open-v1, 1.4B params) |
| **Head** | 5 stacked FastKAN layers, 1536 → 1153 → 770 → 387 → 3 → 3 |
| **Granularity** | Per-residue (one prediction per amino acid) |
| **Classes** | 3 — `0`: non-interface, `1`: interface (binding), `2`: padding |
| **Input** | Peptide (≤50 residues) `|` Protein (≤500 residues), 551 tokens total |
| **Output** | Logits `[B, 3, 551]` → softmax binding probability per residue |
| **Training loss** | Weighted cross-entropy + differentiable geometric distance loss |

## How to Use

### 1. Install the GeoPep code

```bash
git clone https://github.com/Dian0212/GeoPep.git
cd GeoPep
conda create -n geopep python=3.10 -y
conda activate geopep
pip install -r requirements.txt
```

### 2. Download the checkpoint from this repo

```bash
huggingface-cli download dchenqwer/GeoPep model_distanceLoss.ckpt \
    --local-dir model_weights/ --local-dir-use-symlinks False
```

This places the file at `model_weights/model_distanceLoss.ckpt`.

### 3. Run inference on your PDBs

Put PDB files (named `<PDBID>_<peptide_chain>_<protein_chain>.pdb`) into a
folder, then:

```bash
cd scripts
python inference_pipeline.py \
    --pdb-dir /path/to/pdb \
    --checkpoint ../model_weights/model_distanceLoss.ckpt
```

Output: `result/predictions.json` with per-residue binding probabilities.

### 4. Result format

```json
{
  "1a1r_C_A": {
    "peptide_chain": "GSVVIVGRIVLSGKPA",
    "protein_chain": "VEGEVQIVSTATQTFLAT...",
    "peptide_bindingProbability": "0.99 0.99 0.99 ...",
    "protein_bindingProbability": "0.35 0.97 0.12 ..."
  }
}
```

- `peptide_chain` / `protein_chain` — actual residue sequences (padding stripped).
- `*_bindingProbability` — space-separated 2-decimal floats, one per residue.
  Value is the raw class-1 (interface) softmax probability.

## Architecture

```
input tokens [B, 553]                  BOS + 551 residues + EOS
       │
   ESM3 encoder
       ↓ embeddings[:, 1:552, :]       drop BOS / EOS
   [B, 551, 1536]                      per-residue embeddings
       ↓ reshape
   [B * 551, 1536]                     each residue independent
       ↓
   KAN_1: 1536 → 1153
   KAN_2: 1153 → 770
   KAN_3:  770 → 387
   KAN_4:  387 → 3
   KAN_5:    3 → 3
       ↓ reshape + permute
   logits [B, 3, 551]
       ↓ softmax(dim=1)
   binding probability = softmax[:, 1, :]
```

The per-residue head is what makes GeoPep different from the original
CLS-token approach — every residue's embedding flows independently through
the KAN stack, giving sharper position-level predictions.

## Training

- **Dataset**: peptide–protein complexes from the PDB, encoded as
  paired `complex/` (full structure) + `interface/` (binding residues only)
  PDB files.
- **Length filters**: peptide ∈ [10, 50] residues, protein ∈ [10, 500] residues.
- **Loss**:
  - Per-half cross-entropy with class weights `[0.2, 0.8, 0.0]`
    (padding contributes zero gradient).
  - Differentiable distance loss
    `L_dist = Σᵢ P_binding(i) · dist(i) / num_valid_residues`,
    which penalizes high binding probability at residues far from the true
    interface (distance computed from residue centers of mass).
- **Backbone**: ESM3 backbone is fine-tuned together with the KAN head.
- **Optimizer**: AdamW, learning rate 1e-4, weight decay 1e-4.
- **Mixed precision**: FP16.

## Input Format

The model expects a single concatenated string of length 551 tokens:

```
PEPTIDESEQ<pad><pad>...|PROTEINSEQ<pad><pad>...
|<------- 50 ------->|<-------- 500 ----------->|
```

| Position | Content |
|---|---|
| 0 .. 49     | Peptide (left-padded with `<pad>` to 50) |
| 50          | Separator `|` |
| 51 .. 550   | Protein (left-padded with `<pad>` to 500) |

The `inference_pipeline.py` script handles padding and tokenization for you —
you only provide raw PDB files.

## Limitations

- **Sequence-length cap**: peptide must be ≤ 50 residues, protein ≤ 500
  residues. Sequences longer than this are silently skipped at the
  preprocessing stage.
- **Requires per-PDB chain annotation**: filenames must follow the
  `<PDBID>_<peptide_chain>_<protein_chain>.pdb` convention so the pipeline
  knows which chain is the peptide.
- **No uncertainty calibration**: raw softmax probabilities are not calibrated;
  use them as relative scores rather than absolute confidences.
- **Single peptide-protein pair per call**: multi-peptide or multi-chain
  contexts are not supported in the standard pipeline.

## Citation

If you use GeoPep in your work, please cite:

```bibtex
@misc{geopep2026,
  title  = {GeoPep: Geometric-aware Peptide-Protein Binding Site Prediction},
  author = {Chen, Dian},
  year   = {2026},
  howpublished = {\url{https://github.com/Dian0212/GeoPep}}
}
```

## License

MIT