ChEMBL-PDB Linker

Link ChEMBL bioactivity data with PDB structural information to create a curated dataset of protein-ligand pairs with both activity measurements and 3D co-crystal structures. Similar to PDBbind but derived from ChEMBL and PDB directly.

Features

• Validated protein-ligand pairs: Ensures PDB structure contains BOTH the target protein AND the ligand
• Protein-level linking: Connect ChEMBL targets to PDB structures via UniProt IDs
• Ligand-level linking: Match ChEMBL compounds to PDB ligands via InChIKey
• RCSB Search API integration: Efficient bulk queries for ligand-to-structure mappings
• Configurable filters: Activity types (IC50, Ki, Kd), confidence scores, resolution
• Fully reproducible: End-to-end pipeline from raw data to curated output
• Parquet output: Efficient, compressed output format

Expected Output

Running the full pipeline produces:

• ~98,500 validated protein-ligand pairs with bioactivity data
• ~9,000 unique compounds
• ~14,700 unique PDB structures
• ~1,300 unique target proteins

Installation

# Clone the repository
git clone https://github.com/HFooladi/chembl-pdb-linker.git
cd chembl-pdb-linker

# Option 1: Install with uv (recommended)
uv venv
source .venv/bin/activate  # On Windows: .venv\Scripts\activate
uv pip install -e .

# Option 2: Install with pip
python -m venv .venv
source .venv/bin/activate
pip install -e .

Dependencies

• Python >= 3.9
• pandas, pyarrow
• rdkit
• httpx, requests
• typer, pyyaml, tqdm

Quick Start

# Run complete pipeline (downloads ~5GB, takes ~30-60 min)
chembl-pdb-linker run

The output is saved to data/curated/bioactivity_pdb_linked.parquet.

Usage

Command Line

# Run complete pipeline
chembl-pdb-linker run

# Or run steps separately:
chembl-pdb-linker download          # Download ChEMBL, SIFTS, and PDB ligand data
chembl-pdb-linker link              # Link datasets with protein-ligand validation
chembl-pdb-linker extract           # Generate final curated dataset

# Show statistics
chembl-pdb-linker stats

# Use custom config
chembl-pdb-linker run --config my_config.yaml

Python API

from chembl_pdb_linker import Pipeline, Config

# Load config and create pipeline
config = Config.default()
pipeline = Pipeline(config)

# Run complete pipeline
output_path = pipeline.run()

# Or run steps separately
pipeline.download(chembl_version="34")
linked_df = pipeline.link()
output_path = pipeline.extract()

# Get statistics
stats = pipeline.get_statistics()

How It Works

Pipeline Overview

ChEMBL Database ──┬─→ Extract activities (confidence=9) ──┐
                  │                                        │
SIFTS Mapping ────┼─→ UniProt ↔ PDB mapping ──────────────┼──→ Protein-level linking
                  │                                        │
PDB Ligands ──────┼─→ Ligand code ↔ InChIKey mapping ─────┤
                  │                                        │
RCSB Search API ──┴─→ Ligand code → PDB structures ───────┴──→ Validated pairs

Key Algorithm: Protein-Ligand Pair Validation

The critical step is ensuring each linked pair is validated:

1. Protein matching: ChEMBL target → UniProt ID → PDB structures (via SIFTS)
2. Ligand matching: ChEMBL compound → InChIKey → PDB ligand codes
3. Validation: For each potential match, verify the PDB structure contains BOTH the protein AND the ligand

Configuration

Edit config/default.yaml to customize:

chembl:
  confidence_score: 9          # Filter for single-protein targets
  activity_types:              # Activity types to include
    - IC50
    - Ki
    - Kd
    - EC50
  standard_units:
    - nM

pdb:
  max_resolution: 3.5          # Maximum structure resolution (Å)
  rcsb_search_api: "https://search.rcsb.org/rcsbsearch/v2/query"

linking:
  use_inchikey: true           # Match ligands by InChIKey
  inchikey_connectivity_only: false  # Use full InChIKey or just first 14 chars

Output Schema

The final Parquet file (data/curated/bioactivity_pdb_linked.parquet) contains:

Data Sources

• ChEMBL: https://www.ebi.ac.uk/chembl/ - Bioactivity data
• PDB/RCSB: https://www.rcsb.org/ - 3D structures
• SIFTS: https://www.ebi.ac.uk/pdbe/docs/sifts/ - UniProt-PDB mappings
• Ligand Expo: http://ligand-expo.rcsb.org/ - Ligand InChIKey data

Comparison to PDBbind

Citation

If you use this tool in your research, please cite:

@software{chembl_pdb_linker,
  author = {Fooladi, Hosein},
  title = {ChEMBL-PDB Linker: Linking Bioactivity Data with 3D Structures},
  year = {2025},
  publisher = {GitHub},
  url = {https://github.com/HFooladi/chembl-pdb-linker}
}

Please also cite the underlying data sources:

• ChEMBL: Zdrazil, B., et al. (2024). The ChEMBL Database in 2023. Nucleic Acids Research, 52(D1), D1180-D1192.
• PDB: Berman, H.M., et al. (2000). The Protein Data Bank. Nucleic Acids Research, 28(1), 235-242.
• SIFTS: Dana, J.M., et al. (2019). SIFTS: updated Structure Integration with Function, Taxonomy and Sequences resource. Nucleic Acids Research, 47(D1), D482-D489.

License

MIT