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Journal of Bacteriology, August 2008, p. 5153-5161, Vol. 190, No. 15
0021-9193/08/$08.00+0     doi:10.1128/JB.00437-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Complex Regulation of the DnaJ Homolog CbpA by the Global Regulators {sigma}S and Lrp, by the Specific Inhibitor CbpM, and by the Proteolytic Degradation of CbpM {triangledown} ,{dagger}

Matthew R. Chenoweth and Sue Wickner*

Laboratory of Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892

Received 28 March 2008/ Accepted 15 May 2008

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 {Delta}cbpAM {Delta}dnaJ 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, ~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.

* Corresponding author. Mailing address: NCI/NIH, 37 Convent Dr., Rm. 5144, Bethesda, MD 20892. Phone: (301) 496-2629. Fax: (301) 402-1344. E-mail: WicknerS{at}mail.nih.gov

{triangledown} Published ahead of print on 23 May 2008.

{dagger} Supplemental material for this article may be found at http://jb.asm.org/.

Journal of Bacteriology, August 2008, p. 5153-5161, Vol. 190, No. 15
0021-9193/08/$08.00+0     doi:10.1128/JB.00437-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.





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