Figure 4.

Cell cycle regulation by DivL is mediated by CtrA. (A) Phosphorylation of DivK and CtrA by DivJ²⁸⁶ and DivL²⁹⁹. The presence or absence of each protein was indicated as “+” or “−,” respectively. Results of autophosphorylation and phosphotransfer were visualized by autoradiography. (B) Activation of CtrA by DivL kinase. In vitro run-off transcription from the class II flagellar gene fliF promoter was carried out in the presence of reconstituted Caulobacter RNA polymerase containing the sigma factor σ⁷³ (final concentration at 1 μM) as described previously (23). Final concentration of proteins were 10 μM for CtrA and 1 μM for DivL (lanes 1 and 2) and DivJ (lanes 3 and 4). The low-molecular-weight phosphoryl group donor phosphoramidate (PR) was added to the reactions (lanes 5 and 6) at the final concentration of 1 mg/ml. (C) Phase-contrast photomicrograph of cold-sensitive strain PC3407 (divL342; ref 32) at 24°C. (D) Suppression of divL342 by the ctrA allele sokA301 in strain PC3303 (divL342 sokA301 zzz471∷Tn5) at 24°C.