Mu transpososome architecture ensures that unfolding by ClpX or proteolysis by ClpXP remodels but does not destroy the complex

Abstract

The Clp/Hsp100 ATPases are protein unfoldases that both alter protein conformation and target proteins for degradation. An unresolved question has been how such seemingly destructive enzymes can "remodel" some protein substrates rather than destroy them. Here, we investigate the products of ClpX-mediated remodeling of a hyper-stable protein-DNA complex, the Mu transpososome. We find that although an oligomeric complex is maintained, release of some subunits accompanies ClpX action. Replacement of transposase's endogenous ClpX-recognition sequence with an exogenous signal reveals that the mechanism of remodeling is independent of both the recognition signal and the identity of the unfoldase. Finally, examination of the transposase-DNA contacts reveals only a localized region that is altered during remodeling. These results provide a framework for protein remodeling, wherein the physical attributes of a complex can limit the unfolding activity of its remodeler.