Propagated Perturbations from a Peripheral Mutation Show Interactions Supporting WW Domain Thermostability.

Inter-residue interactions stabilize protein folds and facilitate allosteric communication. Predicting which interactions are crucial and understanding why remain challenging. We highlight this through studies of a single peripheral mutation (Q33E) on the surface of the Pin1 WW domain that causes an unexpected loss of thermostability. Nuclear magnetic resonance studies attribute the loss to reorganizations of electrostatic and hydrophobic interactions, resulting in propagated conformational perturbations. The propagation demonstrates the cooperative response of Pin1 WW to external perturbations, consistent with its allosteric behavior within Pin1. Microsecond molecular dynamics simulations suggest the wild-type fold relies on couplings between a surface electrostatic network and a highly conserved hydrophobic core; Q33E directly perturbs the former, thereby disrupting the latter. These couplings suggest that predictions of mutation consequences that assume dominance of a single interaction type can be limiting, and highlight challenges in predicting protein mutational landscapes.