Chaperone-assisted protein folding.

Molecular chaperones of the Hsp70 and chaperonin families are basic constituents of the cellular machinery that mediates protein folding. Recent functional and structural studies corroborate existing models for the mechanism of these components. Highlights of the past year include the X-ray crystallographic analysis of the peptide-binding domain of the Escherichia coli Hsp70 homolog, DnaK, the direct demonstration of protein folding in the central cavity of the chaperonin GroEL, and the visualization of conformational changes in GroEL during the chaperonin folding cycle.