/pdb-database

name: "pdb-database"
description: "Query RCSB PDB (200K+ structures) via the public REST + GraphQL APIs with plain `requests` (no SDK). Search by text, attribute, sequence, or 3D structure similarity (Search API); retrieve metadata via GraphQL (Data API); download PDB/mmCIF from files.rcsb.org. For AlphaFold predictions use alphafold-database-access; for protein sequences only use uniprot-protein-database."
license: "BSD-3-Clause"

PDB Database

> **Why no SDK?** The `rcsb-api` Python SDK is convenient sugar over three public, no-auth REST endpoints (`search.rcsb.org`, `data.rcsb.org`, `files.rcsb.org`). When the SDK is unavailable, every operation can be reproduced with plain `requests` and a small JSON payload. This SKILL.md uses the REST path throughout so the code runs in any environment with `requests` installed.

Overview

RCSB PDB is the worldwide repository for 3D structural data of biological macromolecules with 200,000+ experimentally determined structures. Programmatic access is via three free, no-auth endpoints:

| API | Base URL | Method | Purpose | |---|---|---|---| | **Search** | `https://search.rcsb.org/rcsbsearch/v2/query` | `POST` JSON | Find PDB IDs by text, attribute filters, sequence, or 3D similarity | | **Data** | `https://data.rcsb.org/graphql` | `POST` GraphQL | Retrieve structured metadata (entries, polymer entities, assemblies, ligands) | | **Files** | `https://files.rcsb.org/download/{id}.{format}` | `GET` | Download coordinate files (mmCIF, PDB, FASTA) |

Use this skill for programmatic structural biology queries, drug target analysis, and protein family comparisons.

When to Use

• Searching for protein or nucleic acid crystal/cryo-EM/NMR structures by keyword or property
• Finding structures similar to a query sequence (MMseqs2) or 3D geometry (BioZernike)
• Retrieving experimental metadata (resolution, method, organism, deposition date) for structure sets
• Downloading coordinate files (PDB, mmCIF) for molecular dynamics, docking, or visualization
• Building structure-based datasets for machine learning or drug discovery pipelines
• Comparing protein-ligand complexes across a target family
• For AlphaFold predicted structures, use `alphafold-database-access` instead
• For protein sequence/annotation queries without structures, use `uniprot-protein-database` instead

Prerequisites

• **Python packages**: `requests` (only requirement). Optional: `biopython` for parsing downloaded coordinate files.
• **No API key required**: RCSB PDB is freely accessible.
• **Rate limits**: No published hard limit. Polite delays of `time.sleep(0.2-0.5)` between requests are sufficient; implement exponential backoff on HTTP 429.

pip install requests
# Optional, for coordinate parsing:
pip install biopython

Quick Start

Typical search-then-fetch pattern: hit the Search API, get a list of PDB IDs, then resolve metadata via the GraphQL Data API.

import requests

SEARCH = "https://search.rcsb.org/rcsbsearch/v2/query"
DATA   = "https://data.rcsb.org/graphql"

# 1. Search: human X-ray structures of "kinase" at resolution < 2.0 Å
payload = {
    "query": {
        "type": "group", "logical_operator": "and",
        "nodes": [
            {"type": "terminal", "service": "full_text",
             "parameters": {"value": "kinase"}},
            {"type": "terminal", "service": "text",
             "parameters": {"attribute": "rcsb_entity_source_organism.scientific_name",
                            "operator": "exact_match", "value": "Homo sapiens"}},
            {"type": "terminal", "service": "text",
             "parameters": {"attribute": "rcsb_entry_info.resolution_combined",
                            "operator": "less", "value": 2.0}},
        ],
    },
    "return_type": "entry",
    "request_options": {"paginate": {"rows": 10}},
}
r = requests.post(SEARCH, json=payload, timeout=30)
r.raise_for_status()
result = r.json()
pdb_ids = [hit["identifier"] for hit in result["result_set"]]
print(f"Total matches: {result['total_count']}, first batch: {pdb_ids}")

# 2. Fetch metadata for the first hit via GraphQL
gql = """{ entry(entry_id: "%s") {
  struct { title }
  exptl { method }
  rcsb_entry_info { resolution_combined deposited_atom_count polymer_entity_count }
} }""" % pdb_ids[0]
r2 = requests.post(DATA, json={"query": gql}, timeout=30)
entry = r2.json()["data"]["entry"]
print(entry["struct"]["title"])
print(f"Method: {entry['exptl'][0]['method']}, Resolution: {entry['rcsb_entry_info']['resolution_combined']} Å")

Core API

Module 1: Text and Attribute Search

**Free-text search** uses `service: "full_text"` and searches across all indexed fields.

import requests
SEARCH = "https://search.rcsb.org/rcsbsearch/v2/query"

def text_search(keyword, rows=25):
    payload = {
        "query": {"type": "terminal", "service": "full_text",
                  "parameters": {"value": keyword}},
        "return_type": "entry",
        "request_options": {"paginate": {"rows": rows}},
    }
    r = requests.post(SEARCH, json=payload, timeout=30)
    r.raise_for_status()
    data = r.json()
    return [hit["identifier"] for hit in data["result_set"]], data["total_count"]

ids, total = text_search("hemoglobin")
print(f"Found {total} structures; first batch: {ids[:5]}")

**Attribute search** uses `service: "text"` with structured `attribute`/`operator`/`value` parameters.

import requests
SEARCH = "https://search.rcsb.org/rcsbsearch/v2/query"

def attribute_search(attribute, operator, value, return_type="entry", rows=25):
    payload = {
        "query": {"type": "terminal", "service": "text",
                  "parameters": {"attribute": attribute,
                                 "operator": operator,
                                 "value": value}},
        "return_type": return_type,
        "request_options": {"paginate": {"rows": rows}},
    }
    r = requests.post(SEARCH, json=payload, timeout=30)
    r.raise_fo