Hop, an abundant and conserved protein of unresolved function, binds concomitantly with
heat shock protein 70 (Hsp70) and Hsp90, participates with heat shock proteins at an
intermediate stage of progesterone receptor assembly, and is required for efficient assembly
of mature receptor complexes in vitro. A largely untested hypothesis is that Hop functions as
an adaptor that targets Hsp90-to Hsp70-substrate complexes; if true, then loss of either
Hsp70 binding or Hsp90 binding by Hop should equally disrupt its ability to promote …