Igarashi K, Ishihama A
Department of Molecular Genetics, National Institute of Genetics, Mishima, Shizuoka, Japan.
Cell. 1991 Jun 14;65(6):1015-22. doi: 10.1016/0092-8674(91)90553-b.
The alpha subunit of Escherichia coli RNA polymerase plays a major role in the subunit assembly. Carboxyterminal deletion derivatives lacking 73 or 94 amino acid residues were assembled in vitro into enzyme molecules. Core enzymes consisting of these C-terminal-truncated alpha subunits were as active in RNA synthesis as native core enzyme. By the addition of sigma 70 subunit, these mutant enzymes initiated transcription from certain promoters. The mutant RNA polymerases, however, did not show cAMP-CRP activated transcription. These results demonstrate that the N-terminal region of the alpha subunit is involved in the formation of active enzyme molecule, while the C-terminal region plays an essential role in response to transcription activation by cAMP-CRP.
大肠杆菌RNA聚合酶的α亚基在亚基组装中起主要作用。缺乏73或94个氨基酸残基的羧基末端缺失衍生物在体外组装成酶分子。由这些C末端截短的α亚基组成的核心酶在RNA合成中的活性与天然核心酶相同。通过添加σ70亚基，这些突变酶从某些启动子起始转录。然而，这些突变的RNA聚合酶没有显示出cAMP-CRP激活的转录。这些结果表明，α亚基的N末端区域参与活性酶分子的形成，而C末端区域在响应cAMP-CRP的转录激活中起重要作用。
