We have shown that the 90-kDa heat shock protein (Hsp90) is able to bind partially unfolded firefly luciferase and maintain it in a refoldable state, and that the subsequent successive action of the 20S proteasome activator, PA28, Hsc70 and Hsp40 enables the refolding of the unfolded luciferase. It is most plausible that both the N- and C-terminal chaperone sites of Hsp90 participate in this protein refolding pathway.
