ClpXP degrades the bacterial cell division protein FtsZ

ClpX comprises the ATP‐dependent chaperone component of the ClpXP protease complex. ClpX, a member of the AAA+ ATPase superfamily, assembles into a hexameric ring and binds to a ClpP tetradecamer. Proteins targeted for degradation through the addition of a SsrA tag or specific substrates that contain recognition motifs at the protein termini are recognized by ClpX and translocated into the ClpP protease complex by an ATP‐dependent mechanism. Here, we show that FtsZ, a key requirement for cell division in E. coli and the primary constituent of the cytokinetic Z‐ring, is a substrate for degradation by ClpXP. Recognition of FtsZ by ClpX is localized to the N‐terminal 61 residues of ClpX as a deletion protein, delta61ClpX, is capable of degradation of GFP‐SsrA but deficient for FtsZ degradation. Moreover, we find that GTP, which modulates polymerization of FtsZ in vitro, stimulates the rate of degradation by ClpXP two‐fold, and the specific activity increases with substrate concentration. We propose mechanisms by which ClpXP can interact with FtsZ to modulate an FtsZ polymer population.