Protein Electrostatic Properties are Finetuned Through Evolution

Ionization states play crucial roles in protein functions. Yet despite decades of research, predicting protein pK _a values remains a formidable challenge. Here, we present KaML-ESMs, neural networks built on the ESM protein language models and trained on a synthetically augmented experimental dataset. The KaML-ESMs significantly outperform structure-based approaches for protein pK _a prediction, achieving accuracies approaching experimental resolution across six ionizable amino acids in native proteins. On the most challenging test set of engineered OBTRUDEs (iOnizable suBsTitutions foR bUrieD rEsidues), KaML-ESM2 emerges as the top model, achieving RMSE of 1.36. We applied KaML-ESM2 to the entire human proteome and demonstrated that the predicted pK _a's can identify functional sites and infer catalytic mechanisms. Our work challenges the structure-based paradigm and suggests a view that protein electrostatic properties are encoded in sequence, potentially co-optimized with structure and function through evolution. We offer KaML, a sequence-based end-to-end platform to support applications ranging from biological exploration to drug design, protein engineering, and biomolecular simulations. GAINES, a latent space sampling approach introduced in this work, provides a general framework for addressing data scarcity bottle-necks in machine learning applications.