Department of Microbiology, University of California Davis, Davis, California, United States of America.
PLoS One. 2011;6(9):e25418. doi: 10.1371/journal.pone.0025418. Epub 2011 Sep 29.
The RsbQ α/β hydrolase and RsbP serine phosphatase form a signaling pair required to activate the general stress factor σ(B) of Bacillus subtilis in response to energy limitation. RsbP has a predicted N-terminal Per-ARNT-Sim (PAS) domain, a central coiled-coil, and a C-terminal protein phosphatase M (PPM) domain. Previous studies support a model in which RsbQ provides an activity needed for PAS to regulate the phosphatase domain via the coiled-coil. RsbQ and the PAS domain (RsbP-PAS) therefore appear to form a sensory module. Here we test this hypothesis using bioinformatic and genetic analysis. We found 45 RsbQ and RsbP-PAS homologues encoded by adjacent genes in diverse bacteria, with PAS and a predicted coiled-coil fused to one of three output domains: PPM phosphatase (Gram positive bacteria), histidine protein kinase (Gram negative bacteria), and diguanylate cyclase (both lineages). Multiple alignment of the RsbP-PAS homologues suggested nine residues that distinguish the class. Alanine substitutions at four of these conferred a null phenotype in B. subtilis, indicating their functional importance. The F55A null substitution lay in the Fα helix of an RsbP-PAS model. F55A inhibited interaction of RsbP with RsbQ in yeast two-hybrid and pull-down assays but did not significantly affect interaction of RsbP with itself. We propose that RsbQ directly contacts the PAS domains of an RsbP oligomer to provide the activating signal, which is propagated to the phosphatase domains via the coiled-coil. A similar mechanism would allow the RsbQ-PAS module to convey a common input signal to structurally diverse output domains, controlling a variety of physiological responses.
RsbQ α/β 水解酶和 RsbP 丝氨酸磷酸酶形成了一个信号对，在枯草芽孢杆菌中，当能量受到限制时，它们通过激活一般应激因子 σ(B)来发挥作用。RsbP 具有一个预测的 N 端 Per-ARNT-Sim (PAS)结构域、一个中央卷曲螺旋和一个 C 端蛋白磷酸酶 M (PPM)结构域。先前的研究支持这样一种模型，即 RsbQ 提供了一种活性，这种活性使 PAS 能够通过卷曲螺旋调节磷酸酶结构域。因此，RsbQ 和 PAS 结构域（RsbP-PAS）似乎形成了一个感觉模块。在这里，我们使用生物信息学和遗传分析来检验这一假设。我们发现 45 个 RsbQ 和 RsbP-PAS 同源物由不同细菌中相邻基因编码，其中 PAS 和预测的卷曲螺旋融合到三个输出结构域之一中：PPM 磷酸酶（革兰氏阳性菌）、组氨酸蛋白激酶（革兰氏阴性菌）和双鸟苷酸环化酶（两个谱系）。RsbP-PAS 同源物的多重比对表明，有九个残基可以区分这个类别。这四个残基中的丙氨酸取代在枯草芽孢杆菌中赋予了一个无效表型，表明它们具有功能重要性。F55A 无效取代位于 RsbP-PAS 模型的 Fα 螺旋中。F55A 在酵母双杂交和下拉测定中抑制了 RsbP 与 RsbQ 的相互作用，但对 RsbP 与自身的相互作用没有显著影响。我们提出，RsbQ 直接与 RsbP 寡聚体的 PAS 结构域接触，提供激活信号，该信号通过卷曲螺旋传递到磷酸酶结构域。类似的机制将允许 RsbQ-PAS 模块将一个共同的输入信号传递给结构不同的输出结构域，从而控制各种生理反应。
