Stochastic gating in diffusion-influenced ligand binding to proteins: Gated protein versus gated ligands

The kinetics of the irreversible diffusion-influenced binding of a mobile ligand to a stationary protein is studied, when the ligand concentration is lar er than that of proteins and the efficiency of binding is stochastically gated due to conformational fluctuations of one of the species. A general case of M conformational (gate) states is considered with the goal to better understand the difference between the cases of gated ligand and gated protein discovered for the two gate state model [Zhou and Szabo, J. Phys. Chem. 100, 2597 (1996)]. It is shown that in the former case the binding goes faster than in the latter one.