Evaluating Electrostatic Contributions to Binding with the Use of Protein Charge Ladders

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Science  26 Apr 1996:
Vol. 272, Issue 5261, pp. 535-537
DOI: 10.1126/science.272.5261.535


Electrostatic interactions between charges on ligands and charges on proteins that are remote from the binding interface can influence the free energy of binding (ΔGb). The binding affinities between charged ligands and the members of a charge ladder of bovine carbonic anhydrase (CAII) constructed by random acetylation of the amino groups on its surface were measured by affinity capillary electrophoresis (ACE). The values of ΔGb derived from this analysis correlated approximately linearly with the charge. Opposite charges on the ligand and the members of the charge ladder of CAII were stabilizing; like charges were destabilizing. The combination of ACE and protein charge ladders provides a tool for quantitatively examining the contributions of electrostatics to free energies of molecular recognition in biology.