Protein Symmetry Ring Structure

Constrain protein to form symmetric ring-like multimeric structure

License: This constraint can use multiple tools, each under its own license. See the Tools Used tab and each tool’s page for license details.

This constraint is open source. Any third-party models, product names, or trademarks referenced are the property of their respective owners, and Proto is not affiliated with them.

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Tools Used Tools Used Source Source

proto-bio/proto-language/proto_language/constraint/protein_structure/protein_symmetry_ring_constraint.py

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Constrain proteins to form symmetric ring-like multimeric structures using ESMFold.

This constraint function uses ESMFold to predict multimeric protein structures and evaluates whether they form symmetric ring-like arrangements. Ring symmetry is quantified by calculating the centroid (center of mass) of each protomer’s backbone and measuring how uniformly the protomers are distributed around the ring. Perfect symmetric rings have all inter-protomer distances equal, resulting in zero standard deviation.

Many functional protein complexes naturally form symmetric rings, including chaperonins, proteasomes (heptameric rings), hexameric helicases, and various ring-shaped enzymes. This constraint is useful for designing or selecting proteins that form such symmetric assemblies.

Each input tuple is folded as one complex with an arbitrary number of protein chains. DNA chains are first resolved with ORFipy by scanning both strands for canonical ATG-to-stop ORFs and selecting the longest ORF as that chain’s translated CDS.

Structure prediction is GPU-intensive and may take several minutes per protein depending on length and hardware.

API Reference

ConfigProteinSymmetryRingConfig Source

Configuration for protein symmetry ring constraint.

This class defines configuration parameters for evaluating whether proteins form symmetric ring-like multimeric structures using ESMFold structure prediction. Ring symmetry is measured by analyzing the spatial arrangement of protomer centroids in predicted oligomeric structures. Symmetric rings have protomers evenly distributed in a circular arrangement with consistent inter-protomer distances, characteristic of many functional protein complexes like chaperonins, proteasomes, and ring-shaped enzymes. Symmetry is calculated by taking the centroids of each protomer (using backbone atom coordinates) and measuring the standard deviation of distances between protomers. Lower standard deviation indicates more symmetric arrangements where all protomers are equally spaced. The score is normalized by dividing by max_symmetry_std and capped at 1.0.

max_symmetry_std · number · default: "10.0"

Max std of inter-protomer centroid distances (Å) for normalization; above this gets worst score 1.0.

all_to_all_protomer_symmetry · boolean · default: "False"

True uses pairwise distances between all protomers. Else, use distances between adjacent protomers

esmfold_config · ESMFoldConfig

ESMFold configuration for structure prediction.

ReturnsConstraintOutput

Per-proposal score in [0.0, 1.0] where 0.0 is perfect ring symmetry. Protein results attach the predicted Structure to slot 0. metadata carries:

• avg_plddt: Float average pLDDT score for structure confidence (0.0-1.0)
• ptm: Float predicted TM-score for structure accuracy (0.0-1.0)
• pdb_output: String PDB format structure file content
• esmfolded_sequence: String colon-separated protein-chain representation
• symmetry_std_raw: Float raw standard deviation of inter-protomer distances in Ångströms (lower = more symmetric)
• symmetry_score_normalized: Float normalized symmetry score (0.0-1.0)
• dna_chain_orfs: Per-DNA-chain ORFipy metadata when DNA chains are present

Usage

Designing a symmetric hexameric ring:

python

>>> from proto_language.core import Sequence, SequenceType
>>> seq = Sequence("MVLSPADKTNVKAAWGKVGAHAGEYGAEALERMFLSF", "protein")
>>> config = ProteinSymmetryRingConfig(
...     max_symmetry_std=10.0,
... )
>>> results = protein_symmetry_ring_constraint([(seq, seq, seq, seq, seq, seq)], config)
>>> print(results[0].score)  # e.g., 0.35 (3.5 Å std / 10.0 Å max)
>>> print(results[0].metadata["symmetry_std_raw"])  # e.g., 3.5 Å
>>> print(results[0].metadata["symmetry_score_normalized"])  # 0.35

Metadata

Property	Value
Key	protein-symmetry-ring
Function	protein_symmetry_ring_constraint
Category	protein_structure
Mode	discrete
Uses GPU	True
Supported Types	dna, protein