Regulation of Bacterial Cell Cycle Progression by Redundant Phosphatases

Abstract

Two-component signal transduction systems are widely used by bacteria to adequately respond to environmental changes by adjusting cellular parameters, including the cell cycle. In Caulobacter crescentus , PleC acts as a phosphatase that indirectly protects the response regulator CtrA from premature inactivation during the G 1 phase of the cell cycle. Here, we provide genetic and biochemical evidence that PleC is seconded by another phosphatase, CckN. The activity of PleC and CckN phosphatases is restricted to the G 1 phase since both proteins are degraded by ClpXP protease before the G 1 -S transition. Degradation is independent of any known proteolytic adaptors and relies, in the case of CckN, on an unsuspected N-terminal degron. Our work illustrates a typical example of redundant functions between two-component proteins.