Rondon M R, Escalante-Semerena J C
Department of Bacteriology, University of Wisconsin-Madison 53706, USA.
J Bacteriol. 1996 Apr;178(8):2196-203. doi: 10.1128/jb.178.8.2196-2203.1996.
The PocR protein of Salmonella typhimurium LT2 was overexpressed and used to demonstrate in vitro that it specifically binds to the cobalamin biosynthetic operon (cob) promoter region. Evidence is presented to show that PocR DNA-binding activity in vitro is regulated by the effector molecule 1,2-propanediol. Deletion analysis of the cob promoter (Pcob) suggested that two regions upstream of the promoter are needed for optimal activation of Pcob by PocR in vivo. DNase I footprinting experiments demonstrated that PocR binds to two sites within Pcob. The transcription initiation site of cob mRNA in response to 1,2-propanediol was identified and shown to be different from the one reported for transcription initiation under anoxic conditions in the absence of 1,2-propanediol.
鼠伤寒沙门氏菌LT2的PocR蛋白被过量表达，并用于在体外证明它特异性结合钴胺素生物合成操纵子（cob）的启动子区域。有证据表明，体外PocR的DNA结合活性受效应分子1,2-丙二醇调节。对cob启动子（Pcob）的缺失分析表明，启动子上游的两个区域是PocR在体内最佳激活Pcob所必需的。DNase I足迹实验证明PocR结合在Pcob内的两个位点。确定了响应1,2-丙二醇时cob mRNA的转录起始位点，并表明其与在无氧条件下且不存在1,2-丙二醇时报道的转录起始位点不同。
