alphafold-database-fetch-and-analyze

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---
name: alphafold-database-fetch-and-analyze
description: >
  Retrieve and analyze AlphaFold predicted structures for a protein. Use when
  the user provides a specific UniProt Accession ID and wants structural
  confidence metrics (pLDDT), domain boundary analysis, or disorder
  assessment. Do not use if the user only has a protein name, gene name,
  or amino acid sequence — ask for a UniProt ID first.
---

# AlphaFold Database: Fetch and Analyze

## Prerequisites

1.  **`uv`**: Read the `uv` skill and follow its Setup instructions to ensure
    `uv` is installed and on PATH.
2.  **User Notification**: If
    .licenses/alphafold_database_fetch_and_analyze_LICENSE.txt does not already
    exist in the workspace root directory then (1) prominently notify the user
    to check the terms at https://alphafold.ebi.ac.uk/, then (2) create the file
    recording the notification text and timestamp.

## Overview

Downloads AlphaFold predicted structures (mmCIF) and Predicted Aligned Error
(PAE) matrices from the AlphaFold Database for a given UniProt ID, then performs
automated heuristic analysis on structural confidence (pLDDT), intrinsically
disordered regions, rigid domain boundaries, and inter-domain flexibility.

**Do NOT use when:**

-   The user only has a protein name, gene name, or amino acid sequence (no
    UniProt ID) — ask them to look up the ID on
    [UniProt](https://www.uniprot.org).
-   The user wants to search for structural homologs (use **Foldseek**).
-   The user wants to run AlphaFold predictions on a custom sequence.
-   The user needs experimental PDB structures (use **RCSB PDB**).

## Core Rules

-   **Use the Wrapper**: ALWAYS execute the provided helper scripts to query the
    database rather than accessing the database directly. The scripts
    automatically enforce the required rate limit gracefully.
-   Do not attempt to calculate domain boundaries or assess structural disorder
    yourself; always rely on the output provided by the script.
-   If this skill is used, ensure this is mentioned in the output.

## Utility Scripts

**1. Fetch Structure Files**

Downloads the `.cif` structure file, `_predicted_aligned_error.json`, and API
metadata JSON (`-metadata.json`) for a UniProt ID. Handles fragment fallback for
very large proteins.

Examples:

```bash
uv run scripts/fetch_structure.py P00520 -o /path/to/output/
uv run scripts/fetch_structure.py P04637 -o /path/to/custom_results/
```

Always specify `-o` with an absolute path or a path relative to the user's
project root, never a path relative to the skill directory.

**2. Analyze pLDDT Confidence**

Reads pLDDT confidence metrics from a saved AFDB metadata JSON file (produced by
`fetch_structure.py`) and prints a heuristic confidence assessment (structured,
disordered, mixed).

Example:

```bash
uv run scripts/analyze_plddt.py ./data/AF-P00520-F1-metadata.json
```

**3. Analyze PAE / Domain Boundaries**

Reads a downloaded PAE JSON file and detects rigid domain boundaries using a
sliding-window PAE heuristic.

Example:

```bash
uv run scripts/analyze_pae.py ./data/AF-P00520-F1-predicted_aligned_error_v6.json
```

## Interpreting the Output

The script prints analysis to stdout. Read it carefully and synthesize the
results for the user:

1.  **Isoform / Large Protein Warning (MANDATORY):** Check the script output for
    any `[!] WARNING` lines. If the script reports that no canonical entry was
    found and an isoform was used, or if the protein is very large (>2700 AAs),
    you **MUST** prominently relay this warning to the user. Do not omit this
    warning.
2.  **Synthesize the Structural Analysis**: Combine the "pLDDT Conclusion" and
    the "PAE Structural Conclusion" into a single, cohesive overall summary.
    Describe the protein's overall folding confidence, the presence of
    disordered regions, and its rigid domain layout.
3.  Highlight the supporting metrics:
    -   Overall Global pLDDT and the breakdown of fraction confidence