Polarek J W, Williams G, Epstein W
Department of Biochemistry and Molecular Biology, University of Chicago, Illinois 60637.
J Bacteriol. 1992 Apr;174(7):2145-51. doi: 10.1128/jb.174.7.2145-2151.1992.
The expression of the Kdp system for K+ uptake in Escherichia coli requires the products of two genes, kdpD and kdpE. These genes constitute an operon adjacent to the kdpABC operon that encodes the three membrane protein subunits of Kdp. Both operons are transcribed in the same direction and overlap; the kdpDE promoter is in kdpC, the last gene of the kdpABC operon. Transcription of the kdpDE operon is at a low level when Kdp is not expressed; transcription increases about 10-fold when kdpABC is turned on, indicating significant read-through of the kdpDE operon by transcripts beginning at the promoter of kdpABC operon. The proximal region of the kdpD gene is the site of most mutations that lead to constitutive expression of the kdpABC operon.
大肠杆菌中负责钾离子摄取的Kdp系统的表达需要两个基因kdpD和kdpE的产物。这些基因构成一个与kdpABC操纵子相邻的操纵子，kdpABC操纵子编码Kdp的三个膜蛋白亚基。两个操纵子都沿相同方向转录且相互重叠；kdpDE启动子位于kdpC（kdpABC操纵子的最后一个基因）中。当Kdp不表达时，kdpDE操纵子的转录水平较低；当kdpABC开启时，转录增加约10倍，这表明从kdpABC操纵子启动子开始的转录本对kdpDE操纵子有显著的通读现象。kdpD基因的近端区域是大多数导致kdpABC操纵子组成型表达的突变发生的位点。
