Yamashino T, Kakeda M, Ueguchi C, Mizuno T
Laboratory of Molecular Microbiology, School of Agriculture, Nagoya University, Japan.
Mol Microbiol. 1994 Aug;13(3):475-83. doi: 10.1111/j.1365-2958.1994.tb00442.x.
The Escherichia coli CbpA protein appears to be an analogue of the molecular chaperone, DnaJ, as judged from not only its structure but also its possible function. The expression of cbpA, however, was not significantly affected by up-shift of the growth temperature. Remarkably, it was found that the expression of cbpA was induced under certain growth conditions, such as the entry of cells into stationary phase, or growth in a phosphate-limited medium. Such conditional expression of cbpA was regulated at the transcriptional level in a sigma s-dependent manner. The structure of this sigma s-dependent cbpA promoter was clarified by determining its transcription start site. The cbpA promoter region was found to contain an unusual DNA structure (i.e. DNA curvature). From these results, it was suggested that, in contrast to DnaJ, CbpA may function as a molecular chaperone in an adaptive response to environmental stresses other than heat shock.
从结构和可能的功能来看，大肠杆菌CbpA蛋白似乎是分子伴侣DnaJ的类似物。然而，生长温度上调对cbpA的表达没有显著影响。值得注意的是，发现cbpA的表达在某些生长条件下被诱导，如细胞进入稳定期或在磷酸盐限制培养基中生长。cbpA的这种条件性表达在转录水平上以σs依赖的方式受到调控。通过确定其转录起始位点，阐明了这种σs依赖的cbpA启动子的结构。发现cbpA启动子区域含有异常的DNA结构（即DNA弯曲）。从这些结果推测，与DnaJ不同，CbpA可能在对热休克以外的环境压力的适应性反应中作为分子伴侣发挥作用。
