Thermodynamic Aspects of Coupled Binding and Folding of an Intrinsically Disordered Protein: A Computational Alanine Scanning Study

We have performed computational alanine scanning to gain insight into thermodynamic aspects of coupled Folding and binding of the phosphorylated kinase-inducible activation domain (pKID) of CREB, and intrinsically disorder protein (IDP), to KIX. Residues of pKID directly involved in nativelike interactions at the interface were round to steeply lower their contribution to the free energy of binding. The results suggest that, with a steep lowering of the free energy of binding, it is ensured that pKID has full control of binding specificity, is not trapped in a non-native conformational state, has full plasticity for folding, and forms a thermodynamically stable complex with KIX without compromising binding kinetics.