Sorenson Margareta K, Ray Soumya S, Darst Seth A
The Rockefeller University, 1230 York Avenue, New York, NY 10021, USA.
Mol Cell. 2004 Apr 9;14(1):127-38. doi: 10.1016/s1097-2765(04)00150-9.
The key regulators of bacterial transcription initiation are the sigma factors, which direct promoter recognition and melting but only after binding to the core RNA polymerase to form the holoenzyme. X-ray crystal structures of the flagellar sigma, sigma(28), in complex with its anti-sigma, FlgM, explain the inhibition mechanism of FlgM, including its ability to attack and destabilize the sigma(28)-holoenzyme. The sigma domains (sigma(2), sigma(3), and sigma(4)) pack together in a compact unit with extensive interdomain interfaces that bury the promoter binding determinants, including the -35 element recognition helix of sigma(4), which fits in an acidic groove on the surface of sigma(3). The structure illustrates the large rearrangements that sigma(28) must undergo to form the holoenzyme and provides insights into the regulation of sigma(28) promoter binding activity that may extend, at least in principle, to other sigmas.
细菌转录起始的关键调节因子是σ因子，它们只有在与核心RNA聚合酶结合形成全酶后，才能指导启动子识别和解链。鞭毛σ因子σ（28）与其抗σ因子FlgM形成复合物的X射线晶体结构解释了FlgM的抑制机制，包括其攻击和破坏σ（28）-全酶的能力。σ结构域（σ（2）、σ（3）和σ（4））以紧密的单元形式聚集在一起，具有广泛的结构域间界面，这些界面掩埋了启动子结合决定因素，包括σ（4）的-35元件识别螺旋，该螺旋位于σ（3）表面的酸性凹槽中。该结构展示了σ（28）形成全酶时必须经历的巨大重排，并为σ（28）启动子结合活性的调节提供了见解，这至少在原则上可能扩展到其他σ因子。
