Role of Intrinsically Disordered Regions in Acceleration of Protein-Protein Association

Although intrinsically disordered proteins and intrinsically disordered regions (IDRs) in folded proteins are not able to form stable structures, it is known that they play critically important roles in various biological processes. However, despite multiple studies, the molecular mechanisms of their functions remain not fully understood. In this work, we theoretically investigate the role of IDRs in acceleration of protein-protein association processes. Our hypothesis is that, in protein pairs with several independent binding sites, the association process goes faster if some of these binding sites are located on IDRs or connected by IDRs. To test this idea, we employed analytical modeling, numerical calculations, and Brownian dynamics computer simulations to calculate protein-protein association reaction rates for the ERK2-EtsΔ138 system, belonging to the RAS-RAF-MEK-ERK signaling pathway in living cells. It is found that putting a binding site on IDR accelerates the association process by a factor of 3 to 4. Possible molecular explanations for these observations are presented, and other systems that might use this mechanism are also mentioned.