ProteinMPNN (fixed-backbone sequence design)
Overview
ProteinMPNN (Dauparas et al., Science 2022; dauparas/ProteinMPNN) solves the
inverse-folding problem: given a protein backbone (a 3D structure with no or a
placeholder sequence), it designs amino-acid sequences predicted to fold to that
backbone. It is fast, robust, runs on CPU, and is the standard "sequence" step between
backbone generation (alterlab-rfdiffusion) and structure validation
(alterlab-alphafold).
When to Use This Skill
Use this skill when the user wants to:
- Inverse-fold a backbone PDB into one or more candidate sequences.
- Redesign only selected positions while fixing the rest (partial design).
- Enforce symmetry by tying residues/chains so homo-oligomers get identical sequences.
- Bias the amino-acid composition (e.g. avoid cysteines) or use the soluble model.
- Produce the sequence step of a design → fold → score loop.
Does NOT Trigger
| Scenario | Use instead |
|---|---|
| Design a pocket/interface with a ligand, metal, or nucleic acid present | alterlab-ligandmpnn |
| Generate a new backbone (no starting structure) | alterlab-rfdiffusion |
| Refold a designed sequence to check it (validation) | alterlab-alphafold |
| Generative multimodal (sequence+structure+function) design | alterlab-esm |
Core Capabilities
1. Basic inverse folding
# Parse the PDB, then design sequences (dauparas/ProteinMPNN CLI — TODO(verify) flags/version).
# The parser lives in the repo's helper_scripts directory; run it by name:
python parse_multiple_chains.py --input_path=pdbs/ --output_path=parsed.jsonl
python protein_mpnn_run.py \
--jsonl_path parsed.jsonl --out_folder out/ \
--num_seq_per_target 8 --sampling_temp "0.1"
Lower --sampling_temp (e.g. 0.1) gives conservative, high-confidence designs; higher
temperatures increase diversity. Output FASTA headers carry the model score (lower =
better) and sequence recovery.
2. Fixed positions and chains
Supply a fixed-positions spec (JSONL from the helper scripts) to keep catalytic/known
residues while redesigning the rest, and a chain spec to design only some chains. Verify the
exact helper-script names against your checkout (TODO(verify)).
3. Symmetry / tied positions
Tie positions across chains so a homo-oligomer receives one sequence applied symmetrically —
essential for symmetric alterlab-rfdiffusion outputs.
4. Design → fold → score loop
The canonical de-novo pipeline:
- Generate a backbone with
alterlab-rfdiffusion. - Design sequences for it here (ProteinMPNN), sampling several per backbone.
- Score by refolding each with
alterlab-alphafoldand accepting only self-consistent designs (returns to the target backbone with high pLDDT, low PAE).
Resources
references/proteinmpnn_usage.md— install/pinning, helper-script inputs (fixed positions, tied chains, bias), the soluble model, temperature guidance, and loop integration. Loaded on demand.
Part of the AlterLab Academic Skills suite.