Luk K C, Mark K K
Mol Gen Genet. 1980;178(3):555-60. doi: 10.1007/BF00337860.
The lac transducing phage, lambda plac5, carries a segment of the E. coli lac operon on the left side of the b2 region of the lambda phage. In the absence of additional cyclic AMP, beta-galactosidase can only be expressed from the phage promoter, and the expression of the inserted lac promoter is suppressed. This phage promoter responsible for beta-galactosidase synthesis is shown to be under the control of the cI and N gene products; however, the repressive action of the cro gene product at high multiplicity of infection is not observed although some turn off at very late time is detected. To pin down this phage promoter, results described in this communication and those described elsewhere can rule out the promoter PI, PR, P'R, and the promoter PL also looks rather unlikely. No firm identification of this phage promoter has been made, but the promoter(s) in the b2 region (the b2 promoter) is proposed. The phage promoter responsible for beta-galacrosidase synthesis is shown to be a weak promoter, requires the Q gene product or one (or more) of the late gene products for activation, and the time of expression is very late.
乳糖转导噬菌体λplac5在λ噬菌体b2区域左侧携带一段大肠杆菌乳糖操纵子。在没有额外环磷酸腺苷的情况下，β-半乳糖苷酶只能从噬菌体启动子表达，插入的乳糖启动子的表达受到抑制。负责β-半乳糖苷酶合成的这个噬菌体启动子显示受cI和N基因产物的控制；然而，尽管在非常晚的时间检测到一些关闭现象，但在高感染复数时未观察到cro基因产物的抑制作用。为了确定这个噬菌体启动子，本通讯中描述的结果以及其他地方描述的结果可以排除启动子PI、PR、P'R，启动子PL看起来也不太可能。尚未对这个噬菌体启动子进行确切鉴定，但有人提出b2区域的启动子（b2启动子）。负责β-半乳糖苷酶合成的噬菌体启动子是一个弱启动子，需要Q基因产物或一种（或多种）晚期基因产物来激活，并且表达时间非常晚。
