Role of the sigma subunit of Escherichia coli RNA polymerase in initiation. I. Characterization of core enzyme open complexes.
Role of the sigma subunit of Escherichia coli RNA polymerase in initiation. I. Characterization of core enzyme open complexes.
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大肠杆菌 RNA 聚合酶 sigma 亚基在起始中的作用。
DOI：
10.1016/s0021-9258(18)43428-x
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发表时间：
1980
期刊：
影响因子：
--
通讯作者：
W. R. McClure
中科院分区：
文献类型：
--
作者：
U. Hansen;W. R. McClure
已经表征了大肠杆菌RNA聚合酶核心酶与聚[d（A-T）]-聚[d（A-T）]模板的开放复合物，并与先前表征的相同模板上的全酶开放复合物进行了比较（汉森，U. M.，和麦克卢尔，W. R.（1979）J. Biol. Chem. 254，5713-5717）。通过两种酶催化的二核苷酸pApU的失败起始合成来监测开放复合物。两种复合物的主要区别在于：1）核心酶的UTP米氏常数比全酶高60倍; 2）核心酶与DNA的内在结合常数比全酶低3个数量级; 3）活性需要2个核心单元的协同结合。因此，σ亚基的存在显著改变了开放复合物形成的性质和程度。然而，开放复合物的形成速率对于两种酶都是快速的。利福平显示对核心酶的开放复合物形成的程度具有轻微的刺激作用。
Open complexes of Escherichia coli RNA polymerase core enzyme with a poly[d(A-T)]-poly[d(A-T)]template have been characterized and compared with the previously characterized holoenzyme open complexes on the same template (Hansen, U. M., and McClure, W. R. (1979) J. Biol. Chem. 254, 5713-5717). The open complexes were monitored by the abortive initiation synthesis of the dinucleotide pApU, which is catalyzed by both enzymes. The major differences between the two complexes were: 1) the Michaelis constant for UTP was 60 times higher for core enzyme than for holoenzyme, 2) the intrinsic binding constant of core enzyme to the DNA was 3 orders of magnitude less than that of holoenzyme, and 3) cooperative binding of 2 core units was required for activity. Thus, the presence of the sigma subunit significantly altered the nature and extent of open complex formation. The rate of formation of the open complexes, however, was rapid for both enzymes. Rifampicin is shown to have a slight stimulatory effect on the extent of open complex formation of the core enzyme.