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Non-Canonical Crosslinks Confound Evolutionary Protein Structure Models

Lacombe, R.

2025-03-17 bioinformatics
10.1101/2025.03.17.643596 bioRxiv
Show abstract

Evolution-based protein structure prediction models have achieved breakthrough success in recent years. However, they struggle to generalize beyond evolutionary priors and on sequences lacking rich homologous data. Here we present a novel, out-of-domain benchmark based on sactipeptides, a rare class of ribosomally synthesized and post-translationally modified peptides (RiPPs) characterized by sulfur to -carbon thioether bridges creating cross-links between cysteine residues and backbone. We evaluate recent models on predicting conformations compatible with these cross-links bridges for the 10 known sactipeptides with elucidated post-translational modifications. Crucially, the structures of 5 of them have not yet been experimentally resolved. This makes the task a challenging problem for evolution-based models, which we find exhibit limited performance (0.0% to 19.2% GDT-TS on sulfur to -carbon distance). Our results point at the need for physics-informed models to sustain progress in biomolecular structure prediction.

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