Effect of single point mutations in citrate synthase on binding to GroEL

Abstract

Six single point mutants of yeast citrate synthase were analyzed for binding to the molecular chaperone GroEL. In contrast to the wild-type and G276S, all other G276-mutants were able to displace pre-β-lactamase from GroEL. The off-rate constant for pre-β-lactamase must be at least partially rate-limiting, leading to an equilibrium dissociation constant between 10⁻¹⁰ M and 10⁻¹²M. Direct evidence for binding of citrate synthase was obtained from gel filtration experiments. The results suggest that thermodynamic rather than structural features of the mutants determine the degree of binding to the chaperone.