GroEL AND ITS LIGANDED STATES. Sigler, Paul B., Department of Molecular Biophysics and Biochemistry, Yale University and the Howard Hughes Medical Institute, 295 Congress Ave., New Haven, CT 06510, USA

The bacterial chaperonin, GroEL, is a 14-subunit (60-kD each) double toroidal assembly that assists the folding of proteins in conjunction with a 7-subunit (10 kD each) complex, GroES, and the hydrolysis of Mg^2+-ATP. GroEL/GroES are essential components of E. coli and homologues are found in all eubacteria, archaea and eukaryotic cytoplasmic inclusions. Analogous proteins operate in the cytosol of eukaryotes. Chaperonins function by binding (and, perhaps, unfolding) nonnative proteins in the central cavity of the cylindrical double toroid preventing further misfolding and/or aggregation and releasing them in a form that permits refolding.

The structures of GroEL and its various liganded states will be presented in an effort to provide a structural context for what is known about their role in the folding process and as a basis for the design of genetic and biochemical experiments that further our understanding of the GroEL-assisted folding mechanism.