Facilitated release of substrate protein from prefoldin by chaperonin

Prefoldin is a chaperone that captures a protein-folding intermediate and transfers it to the group 11 chaperonin for correct folding. However, kinetics of interactions between prefoldin and substrate proteins have not been investigated. In this study, dissociation constants and dissociation rate constants of unfolded proteins with prefoldin were firstly measured using fluorescence microscopy. Our results suggest that binding and release of prefoldin from hyperthermophilic archaea with substrate proteins were in a dynamic equilibrium. Interestingly, the release of substrate proteins from prefoldin was facilitated when chaperonin was present, supporting a handoff mechanism of substrate proteins from prefoldin to the chaperonin. (c) 2005 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.