HspBP1, a homologue of the yeast Fes1 and Sls1 proteins, is an Hsc70 nucleotide exchange factor
Résumé
The yeast FES1 and SLS1 genes encode conserved nucleotide exchange factors that act on the cytoplasmic and endoplasmic reticulum luminal Hsp70s, Ssa1p and BiP, respectively. We report here that mammalian HspBP1 is homologous to Fes1p and that HspBP1 promotes nucleotide dissociation from both Ssa1p and mammalian Hsc70. In contrast, Fes1p ine⁄ciently strips nucleotide from mammalian Hsc70, and unlike HspBP1 does not inhibit chaperone-mediated protein re-folding in vitro. Together, our data indicate that HspBP1 is a member of this new class of nucleotide exchange factors that exhibit varying degrees of compartment and species speci¢city. ß 2002 Published by Elsevier Science B.V. on behalf of the Federation of European Biochemical Societies.