CHAPERONE FUNCTION OF HSP90-ASSOCIATED PROTEINS

The Hsp90 heat shock protein of eukaryotic cells regulates the activit y of proteins involved in signal transduction pathways and may direct intracellular protein folding in general. Hsp90 performs at least part of its function in a complex with a specific set of partner proteins that include members of the prolyl isomerase family. The properties of the major components of the Hsp90 complex were examined through the u se of in vitro protein folding assays. Two of the components, FKBP52 a nd p23, functioned as mechanistically distinct molecular chaperones. T hese results suggest the existence of a super-chaperone complex in the cytosol of eukaryotic cells.