Stability Effects of Protein Mutations: The Role of Long-Range Contacts

Predicting the effect of a single point mutation on protein thermodynamic stability (ΔΔ G) is an ongoing challenge with high relevance for both fundamental and applicable aspects of protein science. Drawbacks that limit the predictive power of stability prediction tools include the lack of representations for the explicit energetic terms of the unfolded state. Using coarse-grained simulations and analytical modeling analysis, we found that a mutation that involves the breaking of long-range contacts may lead to an increase in the unfolded state entropy, which can lead to an overall destabilization of the protein. A bioinformatics analysis indicates that the effect of mutation on the unfolded state is greater for hydrophobic or charged (compared with polar) residues that participate in long-range contacts through a loop length longer than 18 amino acids and whose formation probabilities are relatively high.