Murray James W, Delumeau Olivier, Lewis Richard J
Institute for Cell and Molecular Biosciences, Faculty of Medical Sciences, University of Newcastle, Newcastle upon Tyne, UK.
Proc Natl Acad Sci U S A. 2005 Nov 29;102(48):17320-5. doi: 10.1073/pnas.0506599102. Epub 2005 Nov 21.
RsbR is a regulator of sigma(B), the RNA polymerase sigma factor subunit responsible for transcribing the general stress response genes when environmental stress is imposed on Bacillus subtilis. The C-terminal domain of RsbR and its paralogues is a substrate for the kinase function of another sigma(B) regulator, RsbT, but the amino acid sequence of the N-terminal domain of RsbR does not reveal any obvious biochemical function. RsbR, its paralogues, and other regulators of sigma(B), including RsbS and RsbT, form large signaling complexes, called stressosomes. We have determined and present here the crystal structure of the N-terminal domain of RsbR. Unexpectedly, this structure belongs to the globin fold superfamily, but there is no bound cofactor. The globin domain from globin-coupled sensory systems replaces the N-terminal domain of RsbR in some bacteria, indicating a common genetic ancestry for RsbR and the globin family. We suggest that the globin fold has been "recycled" in RsbR and that one more activity can be included in the repertoire of globin functions, namely the ability to bind signaling macromolecules such as RsbT.
RsbR是σB的一种调节因子，σB是RNA聚合酶的σ因子亚基，当枯草芽孢杆菌受到环境压力时，它负责转录一般应激反应基因。RsbR及其旁系同源物的C末端结构域是另一种σB调节因子RsbT激酶功能的底物，但RsbR的N末端结构域的氨基酸序列未显示任何明显的生化功能。RsbR、其旁系同源物以及其他σB调节因子，包括RsbS和RsbT，形成了大型信号复合物，称为应激小体。我们已经确定并在此展示了RsbR的N末端结构域的晶体结构。出乎意料的是，这种结构属于珠蛋白折叠超家族，但没有结合辅因子。来自珠蛋白偶联传感系统的珠蛋白结构域在一些细菌中取代了RsbR的N末端结构域，这表明RsbR和珠蛋白家族有共同的遗传起源。我们认为珠蛋白折叠在RsbR中被“重新利用”，并且珠蛋白功能的全部本领中可以增加一种活性，即结合信号大分子如RsbT的能力。
