Complex regulation of the DnaJ homolog CbpA by the global regulators σS and Lrp, by the specific inhibitor CbpM, and by the proteolytic degradation of CbpM
Complex regulation of the DnaJ homolog CbpA by the global regulators σS and Lrp, by the specific inhibitor CbpM, and by the proteolytic degradation of CbpM
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DOI：
10.1128/jb.00437-08
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发表时间：
2008-08-01
影响因子：
3.2
通讯作者：
Wickner, Sue
中科院分区：
文献类型：
--
作者：
Chenoweth, Matthew R.;Wickner, Sue
CbpA是DnaJ同系物，其作为DnaK共伴侣蛋白发挥功能。一些细胞过程，包括在低温和高温下的生长以及细胞分裂期间的隔膜形成，需要CbpA或DnaJ。CbpA编码在具有CbpM基因的操纵子中，CbpM是CbpA的特异性体内和体外抑制剂。在这里，我们在Delta cbpAM Delta dnaJ菌株中共过表达CbpA和CbpM，并检查了所得的表型。在这些条件下，存在足够的游离CbpA活性以支持在低温下的生长，但在高温下不支持。细胞分裂和λ复制的缺陷，也部分补充了CbpA时，与CbpM cooverexpressed。利用报告融合，我们证明了cbpAM操纵子在从指数生长到稳定期的过渡期最大限度地转录。转录受sigma（S）和Lrp全局调节因子控制，亮氨酸可用性和生长温度都影响转录。CbpA和CbpM在稳定期积累到类似的水平，类似于每个细胞2，300个单体。当不与CbpA结合时，CbpM是不稳定的并且被Lon和ClpAP蛋白酶降解。这些数据表明，CbpA活性在多个水平上受到控制。
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, similar to 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.