Complex regulation of the DnaJ homolog CbpA by the global regulators sigmaS and Lrp, by the specific inhibitor CbpM, and by the proteolytic degradation of CbpM.
CbpA is a DnaJ homolog that functions as a DnaK cochaperone. Several cellular processes, including growth at low and high temperatures and septum formation during cell division, require either CbpA or DnaJ. CbpA is encoded in an operon with the gene for CbpM, which is a specific in vivo and in vitro inhibitor of CbpA. Here, we have cooverexpressed CbpA with CbpM in a DeltacbpAM DeltadnaJ strain and examined the resulting phenotypes. Under these conditions, sufficient free CbpA activity was present to support growth at low temperatures, but not at high temperatures. Defects in cell division and in lambda replication were also partially complemented by CbpA when cooverexpressed with CbpM. Utilizing reporter fusions, we demonstrated that the cbpAM operon was maximally transcribed at the transition from exponential growth to stationary phase. Transcription was controlled by the sigma(S) and Lrp global regulators, and both leucine availability and growth temperature influenced transcription. CbpA and CbpM accumulated to similar levels in stationary phase, approximately 2,300 monomers per cell. When not bound to CbpA, CbpM was unstable and was degraded by the Lon and ClpAP proteases. These data demonstrate that CbpA activity is controlled at multiple levels.
Chenoweth
Matthew R
MR
Laboratory of Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
Wickner
Sue
S
D019677:Artificial Gene Fusion; D001426:Bacterial Proteins / Q000378:metabolism*; D010582:Bacteriophage lambda / Q000254:growth & development; D002352:Carrier Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D002455:Cell Division; D049071:Endopeptidase Clp / Q000235:genetics / Q000378:metabolism; D048168:Escherichia coli K12 / Q000737:chemistry / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D017353:Gene Deletion; D018628:Gene Dosage; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D007930:Leucine / Q000378:metabolism; D051756:Leucine-Responsive Regulatory Protein / Q000378:metabolism*; D049070:Protease La / Q000235:genetics / Q000378:metabolism; D012808:Sigma Factor / Q000378:metabolism*; D013696:Temperature; D001616:beta-Galactosidase / Q000096:biosynthesis / Q000235:genetics
D001426:Bacterial Proteins; D002352:Carrier Proteins; C492508:CbpM protein, E coli; D029968:Escherichia coli Proteins; C497278:Lrp protein, E coli; D012808:Sigma Factor; C069567:sigma factor KatF protein, Bacteria; D051756:Leucine-Responsive Regulatory Protein; D001616:beta-Galactosidase; C483568:ClpA protease, E coli; C483567:Lon protein, E coli; D049070:Protease La; C483572:ClpP protease, E coli; D049071:Endopeptidase Clp; D007930:Leucine