Department of Structural Biology, Weizmann Institute of Science, Rehovot, 76100, Israel
csamir1@weizmann.weizmann.ac.il
A protein engineering approach for detecting and measuring local conformational 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 to probe for changes in pairwise interactions in the chaperonin GroEL during its ATP-induced allosteric transitions. Two pairwise interactions are investigated: one between subunits (Asp41 with Thr522) and the other within subunits (Glu409 with Arg501). We find that the intra-ring inter-subunit interaction between Asp41 and Thr522 changes little during the allosteric transitions of GroEL indicating that the hydrogen bond between these residues is maintained. In contrast, the intra-subunit salt-bridge between Glu409 and Arg501 becomes weaker during the ATP-induced allosteric transitions of GroEL. Our results are consistent with the electron microscopy observations of an ATP-induced hinge movement of the apical domains relative to the equatorial domains.