Role of side-chains in the operation of the main molecular hinge of 3-phosphoglycerate kinase.

The single mutants (F165A, E192A, F196A, S392A, T393A) at and near the main hinge (beta-strand L) of human 3-phosphoglycerate kinase (hPGK) exhibit variously reduced enzyme activity, indicating the cumulative effects of these residues in regulating domain movements. The residues F165 and E192 are also essential in maintaining the conformational integrity of the whole molecule, including the hinge-region. Shortening of betaL by deleting T393 has led to a dramatic activity loss and the concomitant absence of domain closure (as detected by small angle X-ray scattering), demonstrating the role of betaL in functioning of hPGK. The role of each residue in the conformational transmission is described.