Binding of methylumbelliferyl mannoside to concanavalin a under high pressure

Abstract

The equilibrium binding of 4-methylumbelliferyl α- d-mannopyranoside to concanavalin A was measured by changes in fluorescence quenching observed at pressures ranging from 1 to 2000 bar (1974 atmospheres). From the pressure-induced changes in the apparent K a, we calculated volume changes for the association reaction of −2.5 and −1.7 ± 1 ml/mol for concanavalin A in its dimeric and tetrameric forms, respectively. This carbohydrate-binding reaction is less pressure-sensitive than other protein-ligand interactions that have been studied under pressure. The volume change observed is comparable to that expected for a reaction involving hydrogen bond formation, in a non-polar environment.