The CckA-ChpT-CtrA-CpdR signaling pathway controls cell cycle progression in Caulobacter. A. Schematic of the CckA-ChpT-CtrA-CpdR signaling pathway. B. Domain organization of the TCS proteins in the CckA-ChpT-CtrA-CpdR pathway (transmembrane helix, TM; Per-Arnt-Sim sensor domain, PAS; dimerization and histidine phosphotransfer domain, DHp; catalytic and ATP-binding domain, CA; receiver domain, RD; helix-turn-helix DNA binding domain, HTH; domain of unknown function, DUF). Vertical arrows point to residues involved in phosphotransfer.