Rhodius V A, West D M, Webster C L, Busby S J, Savery N J
School of Biochemistry, University of Birmingham, PO Box 363, Birmingham B15 2TT, UK.
Nucleic Acids Res. 1997 Jan 15;25(2):326-32. doi: 10.1093/nar/25.2.326.
Transcription activation by the Escherichia coli cyclic AMP receptor protein (CRP) at Class II promoters is dependent on direct interactions between two surface-exposed activating regions (AR1 and AR2) and two contact sites in RNA polymerase. The effects on transcription activation of disrupting either AR1 or AR2 have been measured at different Class II promoters. AR2 but not AR1 is essential for activation at all the Class II promoters that were tested. The effects of single positive control substitutions in AR1 and AR2 vary from one promoter to another: the effects of the different substitutions are contingent on the -35 hexamer sequence. Abortive initiation assays have been used to quantify the effects of positive control substitutions in each activating region on the kinetics of transcription initiation at the Class II CRP- dependent promoter pmelRcon. At this promoter, the HL159 substitution in AR1 results in a defect in the initial binding of RNA polymerase whilst the KE101 substitution in AR2 reduces the rate of isomerization from the closed to the open complex.
大肠杆菌环腺苷酸受体蛋白（CRP）在II类启动子处的转录激活取决于两个表面暴露的激活区域（AR1和AR2）与RNA聚合酶中的两个接触位点之间的直接相互作用。在不同的II类启动子上已测量了破坏AR1或AR2对转录激活的影响。在所有测试的II类启动子中，AR2而非AR1对于激活至关重要。AR1和AR2中单个阳性对照替代的影响因启动子而异：不同替代的影响取决于-35六聚体序列。已使用流产起始测定法来量化每个激活区域中的阳性对照替代对II类CRP依赖性启动子pmelRcon处转录起始动力学的影响。在该启动子处，AR1中的HL159替代导致RNA聚合酶初始结合缺陷，而AR2中的KE101替代降低了从封闭复合物到开放复合物的异构化速率。
