The bacterial class IIIb adenylate cyclase CyaC-Sm of Sinorhizobium meliloti: Redox sensing by a heme B binding membrane anchor

苜蓿中华根瘤菌的细菌 IIIb 类腺苷酸环化酶 CyaC-Sm：通过血红素 B 结合膜锚进行氧化还原传感

• 批准号: 361006731
• 负责人: Professor Dr. Gottfried Unden
• 金额: --
• 依托单位: Mikrobiologie und Weinforschung
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2017
• 资助国家: 德国
• 起止时间: 2016-12-31 至 2019-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/361006731?language=en
• 关键词: bacterial; class; IIIb; adenylate; cyclase

Pro- and eukaryotic adenylate cyclases: Membrane anchors with sensory function?Adenylate cyclases (AC) producing the second messenger cyclic AMP from ATP are present in all classes of life (eukarya, bacteria and archaea). Cyclic AMP has a broad significance in regulating cellular functions. The AC enzymes are grouped in six classes, and the best characterized ACs are members of class III which covers most eukaryotic and bacterial ACs. The ACs of this class show a large variation in domain composition, signal perception, regulation and overall function. The proposal aims at understanding the function of CyaC-Sm of Sinorhizobium meliloti, a class IIIb AC, and the role of its hexa-helical (6-TM) membrane anchor in redox sensing. A 6-TM membrane anchor is conserved in the eukaryotic (including mammalian) and some bacterial class III ACs. Bacterial ACs of this design have not been characterized in molecular detail. Understanding CyaC-Sm may have an impact on assessing the membrane anchor and its potential sensory role in eukaryotic class III ACs. Preparatory work suggests that CyaC-Sm contains a quinone reactive heme B in the membrane anchor. Respiration and quinones are supposed to oxidize the heme B and an iron-sulfur cluster in a ferredoxin-type domain and, as a result, to control dimerization and activity of the catalytic domain. The membrane anchor with the quinone/heme site and the near-by FeS cluster show a remarkable similarity to domains of the well-characterized respiratory fumarate reductase in structural and functional terms. The role of the components and of a linked oxidoreductase (SMc01816) in controlling AC activity will be charac-terized with purified CyaC-Sm, and by the use of wild-type and mutant CyaC-Sm expressed in E. coli. Overall, the study aims at characterizing function and molecular details of CyaC-Sm as a novel, actually the first, redox-controlled class III adenylate cyclase. The work might be of broader significance by assigning the hexa-helical TM domain of AC proteins a sensory role which is also discussed for membrane-delimited eukaryotic ACs. The physiological role of CyaC-Sm in S. meliloti is not analyzed in the proposal. However, there are first indications that CyaC-Sm is linked to aerobic respiration and to denitrification.

原和真核腺苷环化酶：具有感官功能的膜锚？腺苷环化酶(AC)从三磷酸腺苷(ATP)产生第二信使环状AMP，存在于所有生物(真核生物、细菌和古生物)。环磷酸腺苷在调节细胞功能方面具有广泛的意义。AC酶分为六类，其中特征最好的AC是第III类成员，它涵盖了大多数真核和细菌AC。这类AC在域组成、信号知觉、调节和整体功能方面表现出很大的差异。该提案旨在了解苜蓿中华根瘤菌的CyaC-Sm的功能，以及其六螺旋(6-TM)膜锚在氧化还原传感中的作用。6-TM膜锚点在真核生物(包括哺乳动物)和一些细菌III类ACS中是保守的。这种设计的细菌型ACS还没有在分子细节上得到表征。了解CyaC-Sm可能会对评估膜锚定及其在真核细胞III类ACS中的潜在感觉作用产生影响。前期工作表明，CyaC-Sm的膜锚中含有苯醌反应性血红素B。呼吸作用和苯二酚被认为是氧化血红素B和铁还蛋白类型结构域中的铁硫簇，结果是控制催化结构域的二聚化和活性。带有苯醌/血红素位点和邻近FeS簇的膜锚定在结构和功能上与特征很好的呼吸性富马酸还原酶的结构域具有显著的相似性。我们将用纯化的CyaC-Sm和在大肠杆菌中表达的野生型和突变型CyaC-Sm来表征这些成分和连接的氧化还原酶(SMc01816)在控制AC活性中的作用。总体而言，本研究旨在研究CyaC-Sm作为一种新的、实际上是第一个由氧化还原控制的III类腺苷环化酶的功能和分子细节。这项工作可能具有更广泛的意义，因为它赋予AC蛋白的六螺旋TM结构域一个感觉角色，这也是对膜分隔的真核细胞ACS的讨论。该提案没有分析CyaC-Sm在苜蓿链霉菌中的生理作用。然而，有初步迹象表明，CyaC-Sm与好氧呼吸和反硝化作用有关。