Abstract
AAA(+) chaperone ClpX has been suggested to be a modulator of prokaryotic cytoskeletal protein FtsZ, but the details of recognition and remodeling of FtsZ by ClpX are largely unknown. In this study, we have extensively investigated the nature of FtsZ polymers and mechanisms of ClpX-regulated FtsZ polymer dynamics. We found that FtsZ polymerization is inhibited by ClpX in an ATP-independent manner and that the N-terminal domain of ClpX plays a crucial role for the inhibition of FtsZ polymerization. Single molecule analysis with high speed atomic force microscopy directly revealed that FtsZ polymer is in a dynamic equilibrium between polymerization and depolymerization on a time scale of several seconds. ClpX disassembles FtsZ polymers presumably by blocking reassembly of FtsZ. Furthermore, Escherichia coli cells overproducing ClpX and N-terminal domain of ClpX show filamentous morphology with abnormal localization of FtsZ. These data together suggest that ClpX modulates FtsZ polymer dynamics in an ATP-independent fashion, which is achieved by interaction between the N-terminal domain of ClpX and FtsZ monomers or oligomers.