Disassembly and degradation of MinD oscillator complexes by Escherichia coli ClpXP

MinD is a cell division ATPase in Escherichia coli that oscillates from pole to pole and regulates the spatial position of the cell division machinery. Together with MinC and MinE, the Min system restricts assembly of the FtsZ-ring to midcell, oscillating between the opposite ends of the cell and preventing FtsZ-ring misassembly at the poles. Here, we show that the ATP-dependent bacterial proteasome complex ClpXP degrades MinD in reconstituted degradation reactions in vitro, through direct recognition of the MinD N-terminal region, and in vivo. MinD degradation is enhanced during stationary phase, suggesting that ClpXP regulates levels of MinD in cells that are not actively dividing. MinC and MinD are known to co-assemble into linear polymers, therefore we monitored copolymers assembled in vitro after incubation with ClpXP and observed that ClpXP promotes rapid MinCD copolymer disassembly as a result of direct MinD degradation by ClpXP. The N-terminus of MinD, including residue Arg 3, which is near the ATP-binding site, is critical for degradation by ClpXP. Together, these results demonstrate that ClpXP degradation modifies conformational assemblies of MinD in vitro and depresses Min function in vivo during periods of reduced proliferation.