Single-molecule binding dynamics and cooperativity of the first two cyclic nucleotides at the TAX-4 CNG channel

Abstract

Binding of ligands to multiple active sites in oligomeric proteins is an important phenomenon for many biological processes. The kinetics of distinct binding events directly relate to the energetics of conformational changes underlying both binding and cooperative interactions between sites. However, these dynamics are rarely directly observed and are occluded in ensemble measures due to averaging over mixtures of bound conformations and asynchronous events. Single-molecule (SM) approaches are powerful tools for resolving these asynchronous dynamics, but their application to studies of membrane proteins is challenged by costly sample preparation, degradation of protein function in nonnative lipid environments such as detergents, and lack of solution access to intracellular binding sites.