Ramani N, Huang L, Freundlich M
Department of Biochemistry and Cell Biology, State University of New York, Stony Brook 11794-5215.
Mol Gen Genet. 1992 Jan;231(2):248-55. doi: 10.1007/BF00279798.
Previous work has shown that integration host factor (IHF) mutants have increased expression and altered osmoregulation of OmpF, a major Escherichia coli outer membrane protein. By in vitro analysis the possibility was investigated that IHF interacts directly with the ompF promoter region. Gel retardation assays and DNase I protection experiments showed that IHF binds to two sites in the ompF promoter region centered at positions -180 and -60 relative to the start of transcription. Gel electrophoresis studies with circularly permuted ompF promoter fragments indicated that IHF binding strongly increased a small intrinsic bend in the ompF promoter region. The addition of IHF to a purified in vitro transcription system strongly and specifically inhibited ompF transcription. This inhibition was reversed by increasing the concentration of OmpR, a positive activator required for ompF expression, suggesting that IHF may inhibit ompF transcription by altering how OmpR interacts with the ompF promoter.
先前的研究表明，整合宿主因子（IHF）突变体可使大肠杆菌主要外膜蛋白OmpF的表达增加并改变其渗透压调节。通过体外分析，研究了IHF是否直接与ompF启动子区域相互作用。凝胶阻滞分析和DNase I保护实验表明，IHF与ompF启动子区域中相对于转录起始位点位于-180和-60位置的两个位点结合。对环形排列的ompF启动子片段进行的凝胶电泳研究表明，IHF的结合强烈增加了ompF启动子区域的一个小的固有弯曲。将IHF添加到纯化的体外转录系统中会强烈且特异性地抑制ompF转录。通过增加ompF表达所需的正激活因子OmpR的浓度可逆转这种抑制作用，这表明IHF可能通过改变OmpR与ompF启动子的相互作用方式来抑制ompF转录。
