ENHANCEMENT OF PROTEIN-PROTEIN ASSOCIATION RATE BY INTERACTION POTENTIAL - ACCURACY OF PREDICTION BASED ON LOCAL BOLTZMANN FACTOR

Electrostatic interactions are known experimentally to enhance the rat e of protein-protein association by three to four orders of magnitude. However, theoretical efforts to quantitatively account for such rate enhancement have been hampered by the need to consider a large number of relative configurations of two associating proteins sampled during their diffusional encounter. Our recent work indicates that a good est imate of the rate enhancement is given by the average Boltzmann factor in the region of configurational space where association can effectiv ely take place. This estimate is tested on a model system consisting o f two spherical proteins, each with a ''reactive patch.'' Three differ ent forms of interaction potential are considered. Comparison with exa ct results for the association rate constant demonstrates that predict ions based on the local Boltzmann factor are accurate to within simila r to 50% for realistic sizes of the reactive region and amplitudes of the interaction potential.