Mechanistic Basis for Site–Site Interactions in Inhibitor and Substrate Binding to Band 3 (AE1): Evidence Distinguishing Allosteric from Electrostatic Effects

Kinetic studies suggest that stilbenedisulfonates inhibit erythrocyte anion exchange by competing with substrate anions for binding to band 3 (AE1). Such competition seems to involve site–site interactions between distinct inhibitor and substrate binding sites. The molecular basis for site–site interactions could be allosteric or electrostatic. In this paper, inhibitor binding kinetic studies are reviewed, and 35Cl− NMR line-broadening experiments are presented, both of which seem to rule out an electrostatic hypothesis. The results are consistent with an allosteric site–site interaction mechanism in the binding of stilbenedisulfonate and substrate anions to band 3.