Arm-in-Arm Response Regulator Dimers Promote Intermolecular Signal Transduction
Arm-in-Arm Response Regulator Dimers Promote Intermolecular Signal Transduction
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DOI：
10.1128/jb.00872-15
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发表时间：
2016-04-01
影响因子：
3.2
通讯作者：
Forest, Katrina T.
中科院分区：
文献类型：
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作者：
Baker, Anna W.;Satyshur, Kenneth A.;Forest, Katrina T.
细菌光敏色素光感受器（BphP）及其同源反应调节器组成了双组分信号转导系统，引导细菌对环境光质量的变化产生表型反应。这些系统大多数利用单域响应调节器通过未知的途径和机制来转换信号。在这里，我们描述了 RtBphP1 的光循环和自磷酸化动力学，RtBphP1 是一种来自沙漠细菌 Ramlibacter tataouinensis 的红光调节组氨酸激酶。 RtBphP1 经历红色到远红色的光转换，并快速热回复到暗态。 RtBphP1 在黑暗中自磷酸化；该活性在红光下被抑制。 RtBphP1 同源反应调节剂、R. tataouinensis 细菌光敏色素反应调节剂 (RtBRR) 和来自根癌农杆菌的同源物 AtBRR，意外地结晶为臂对臂二聚体，依赖于保守的疏水基序 hFWAhL（其中 h 是疏水性 M、V、L 或 I 残基）。 RtBRR 和 AtBRR 的二聚体与光合生物中发现的四种结构特征光敏色素反应调节剂以及蛋白质数据库中的所有其他受体域同二聚体截然不同。独特的二甲胂酸锌组氨酸标签金属有机框架产生单波长异常衍射相，可能引起普遍关注。 BRR 化学计量对信号转导影响的检查表明，磷酸化 RtBRR 在磷酸转移反应中比工程化单体 RtBRR (RtBRR(mon)) 更有效地积累。因此，我们得出结论，臂夹臂二聚体是此类双组分调节系统中的相关信号传导中间体。重要性BphP 组氨酸激酶及其同源反应调节剂组成了广泛的红光感应双组分系统。关于 BphP 的许多工作都集中在光传感的结构理解和增强这些蛋白质的天然红外荧光上，而不是信号转导或由此产生的表型。为了开始解决这一知识差距，我们解决了两个单域响应调节器的晶体结构，该调节器由编码 BphP 的紧下游区域编码。我们观察到了以前未知的臂臂二聚体连接。通过删除 C 端二聚化基序进行的单体化对净响应调节因子磷酸化具有抑制作用，强调了这些不寻常的二聚体对于信号转导的重要性。
Bacteriophytochrome photoreceptors (BphPs) and their cognate response regulators make up two-component signal transduction systems which direct bacteria to mount phenotypic responses to changes in environmental light quality. Most of these systems utilize single-domain response regulators to transduce signals through unknown pathways and mechanisms. Here we describe the photocycle and autophosphorylation kinetics of RtBphP1, a red light-regulated histidine kinase from the desert bacterium Ramlibacter tataouinensis. RtBphP1 undergoes red to far-red photoconversion with rapid thermal reversion to the dark state. RtBphP1 is autophosphorylated in the dark; this activity is inhibited under red light. The RtBphP1 cognate response regulator, the R. tataouinensis bacteriophytochrome response regulator (RtBRR), and a homolog, AtBRR from Agrobacterium tumefaciens, crystallize unexpectedly as arm-in-arm dimers, reliant on a conserved hydrophobic motif, hFWAhL (where h is a hydrophobic M, V, L, or I residue). RtBRR and AtBRR dimerize distinctly from four structurally characterized phytochrome response regulators found in photosynthetic organisms and from all other receiver domain homodimers in the Protein Data Bank. A unique cacodylate-zinc-histidine tag metal organic framework yielded single-wavelength anomalous diffraction phases and may be of general interest. Examination of the effect of the BRR stoichiometry on signal transduction showed that phosphorylated RtBRR is accumulated more efficiently than the engineered monomeric RtBRR (RtBRR(mon)) in phosphotransfer reactions. Thus, we conclude that arm-in-arm dimers are a relevant signaling intermediate in this class of two-component regulatory systems.IMPORTANCEBphP histidine kinases and their cognate response regulators comprise widespread red light-sensing two-component systems. Much work on BphPs has focused on structural understanding of light sensing and on enhancing the natural infrared fluorescence of these proteins, rather than on signal transduction or the resultant phenotypes. To begin to address this knowledge gap, we solved the crystal structures of two single-domain response regulators encoded by a region immediately downstream of that encoding BphPs. We observed a previously unknown arm-in-arm dimer linkage. Monomerization via deletion of the C-terminal dimerization motif had an inhibitory effect on net response regulator phosphorylation, underlining the importance of these unusual dimers for signal transduction.