Long-Range Electrostatic Contributions to Protein−Ligand Binding Estimated Using Protein Charge Ladders, Affinity Capillary Electrophoresis, and Continuum Electrostatic Theory

Affinity capillary electrophoresis and protein charge ladders are used together to measure the contributions of long-range electrostatic interactions to binding of substituted benzene sulfonamide inhibitors to derivatives of human carbonic anhydrase II. The results are analyzed by continuum electrostatic calculations, which afford a detailed analysis of interactions of individual members of a population from a charge ladder. A Monte Carlo simulation of the experimental data using calculated contributions of individual lysine side chains to inhibitor binding shows that a large number of different patterns of acetylation are consistent with the experimental results. The calculations predict significant differences in the contributions of some lysines to ΔG and simulations suggest that experimental resolution must be enhanced to be able to measure such differences.