The C-terminal sequence of the chaperonin GroES is required for oligomerization

The Escherichia coli protein GroES is a co-chaperonin that is able to assist GroEL in the refolding of proteins. GroES is a heptamer of seven identical subunits. Recent work has focused on the structural aspects of GroES. We have investigated the role of the C-terminal portion of GroES on its oligomerization. Limited proteolysis of GroES by carboxypeptidase Y gives a product in which the C-terminal 7 amino acid residues have been removed. Sedimentation velocity analysis reveals that the truncated form of GroES is unable to reassemble. The results presented here implicate the C-terminal sequence in intermonomer actions within the GroES oligomer. In addition, this work provides experimental verification of predictions implied in the recent x-ray determination of the GroES structure (Hunt, J. F., Weaver, A. J., Landry, S. J., Gierasch, L. M., and Deisenhofer, J. Nature, in press).