Ghersa P, Lurz R, Dobrinski B, Deshusses J, Belet M, Frey J
Département de Biochimie, Université de Genève, Switzerland.
Mol Gen Genet. 1988 Jul;213(1):36-41. doi: 10.1007/BF00333395.
The plasmid ColD-CA23, a high copy number plasmid of 5.12 kb, contains genes for colicin D (cda), for immunity colicin D (cdi), and for a lysis function (cdl). These genes are arranged on a contiguous 2.4 kb fragment in the following sequence: cda, cdi, cdl. They are transcribed in two operons, one transcribing cda and cdl from a SOS inducible promoter, the other transcribing cdi in the opposite direction. The expression of cda and cdl is modulated by a repressor, cdr, which is encoded on the same transcript as cda and cdl. In the absence of this repressor, transcription from the SOS inducible colicin D promoter is exceptionally strong and leads to protein contents up to 50% of total cellular proteins. This autoregulative repressor is a new finding in the control mechanisms of expression of colicins. We have also identified the gene product of cdl to be a 10,000 dalton protein.
质粒ColD-CA23是一个5.12 kb的高拷贝数质粒，含有大肠杆菌素D（cda）、大肠杆菌素D免疫蛋白（cdi）以及裂解功能蛋白（cdl）的基因。这些基因以cda、cdi、cdl的顺序排列在一个连续的2.4 kb片段上。它们由两个操纵子转录，一个从SOS诱导型启动子转录cda和cdl，另一个以相反方向转录cdi。cda和cdl的表达受阻遏物cdr调控，cdr与cda和cdl在同一转录本上编码。在没有这种阻遏物的情况下，来自SOS诱导型大肠杆菌素D启动子的转录异常强烈，导致蛋白质含量高达细胞总蛋白的50%。这种自动调节阻遏物是大肠杆菌素表达控制机制中的一个新发现。我们还确定cdl的基因产物是一种10,000道尔顿的蛋白质。
