Hop is a 60-kDa protein characterized by its ability to bind the two chaperones, hsp70 and
hsp90. We have tested the function of Hop using an assay for the refolding of denatured
firefly luciferase. We show that Hop is involved in the process of refolding thermally
denatured firefly luciferase in rabbit reticulocyte lysate. Hop also stimulates refolding by
hsp70 and Ydj-1 in a purified refolding system. Hsp90 can also stimulate refolding, and
optimal refolding is observed in the presence of both Hop and hsp90. Similar stimulation …