DETECTION OF CHANGES IN PAIRWISE INTERACTIONS DURING ALLOSTERIC TRANSITIONS - COUPLING BETWEEN LOCAL AND GLOBAL CONFORMATIONAL-CHANGES IN GROEL

A protein engineering approach for detecting and measuring local confo rmational changes that accompany allosteric transitions in proteins is described, Using this approach, we can identify interactions that are made or broken during allosteric transitions, The method is applied t o probe for changes in pairwise interactions in the chaperonin GroEL d uring its ATP-induced allosteric transitions, Two pairwise interaction s are investigated: one between subunits (Asp-41 with Thr-522) and the other within subunits (Glu-409 with Arg-501), We find that the intrar ing intersubunit interaction between Asp-41 and Thr-522 changes little during the allosteric transitions of GroEL, indicating that the hydro gen bond between these residues is maintained. In contrast, the intras ubunit salt bridge between Glu-409 and Arg-501 becomes significantly w eaker during the ATP-induced allosteric transitions of GroEL, Our resu lts are consistent with the electron microscopy observations of an ATP -induced hinge movement of the apical domains relative to the equatori al domains.