MUTATION ALA2 -] SER DESTABILIZES INTERSUBUNIT INTERACTIONS IN THE MOLECULAR CHAPERONE GROEL

The mutation Ala2 → Ser in the molecular chaperone GroEL increases positive co-operativity in ATP hydrolysis, as reflected by a change in the Hill coefficient from 2.36(±0.23) for wild-type to 3.19(±0.17) for the mutant. This amino acid replacement destabilizes the oligomeric structure of GroEL. It is shown that adenine nucleotides also have a specific destabilizing effect which is more pronounced in the case of the Ala2 → Ser mutant. Addition of GroES or the non-folded protein ligand rhodanese blocks the destabilizing effect of adenine nucleotides for both wild-type and mutant. The results are interpreted using the Monod-Wyman-Changeux (MWC) model for co-operativity. © 1993 Academic Press, Inc.