Magnesium Homeostasis in Microorganisms

微生物中的镁稳态

基本信息

批准号：
7889204
负责人：
MICHAEL E MAGUIRE
金额：
$ 13.62万
依托单位：
CASE WESTERN RESERVE UNIVERSITY
依托单位国家：
美国
项目类别：
财政年份：
2009
资助国家：
美国
起止时间：
2009-08-31 至 2011-06-30
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/7889204
关键词：
ATP phosphohydrolase Amino Acid Sequence Antibiotics Apoptosis Archaea Back Binding Binding Sites Biological Biological Assay Carrier Proteins Cations Cells Charge Chemistry Crystallization Cytoplasmic Tail Cytosol Dehydration Elements Employee Strikes Eubacterium Eukaryota Eukaryotic Cell Family Family member Growth Health Homeostasis Homologous Gene Housekeeping Hydroxyl Radical Ions Length Link Lipid Bilayers Magnesium Manuscripts Mass Spectrum Analysis Mediating Membrane Mitochondria Mutation Nature Neck Orthologous Gene Phenotype Physiological Progress Reports Prokaryotic Cells Proteins Regulation Resolution Role Salmonella enterica Salmonella typhimurium Shapes Side Site-Directed Mutagenesis Structure Surface System Testing Thermotoga Thermotoga maritima Transmembrane Domain Virulence Virulence Factors Work attenuation base extracellular insight member microorganism monomer novel periplasm research study uptake

项目摘要

Mg chemistry is unique among biological cations, and cells possess novel mechanisms for regulating Mg2+ and facilitating its passage through membranes. This proposal focuses on the CorA Mg2+ transporter, the primary Mg2+ uptake system for most Eubacteria and Archaea. The crystal structure of CorA from Thermotoga maritime has been determined to 3.9 A resolution. It is a funnel-shaped homopentamer with two transmembrane (TM)helices. The extracellular region is composed of only a short conserved loop that connects the two TM helices. The channel is composed of five helices, one from each monomer and appears gated by the side chains of bulky hydrophobic residues within the pore. These helices extend well beyond the membrane through the cytoplasmic domain, forming the funnel inner surface. Outside the funnel, the cytoplasmic neck of the pore is surrounded by a ring of highly conserved positively charged residues. Two negatively charged helices in the cytoplasmic domain extend back towards the membrane outside the funnel and abut the ring of positive charge. These exterior helices may serve to counteract the positively charged ring, suggesting a gating mechanism. An apparent Mg2+ ion was bound in the cytoplasmic domain between monomers, linking the extended helix from one monomer to a set of helices in another. The Mg2+ binding site, conserved in CorA orthologs, may link pore opening to the intracellular concentration of Mg2+. Aim 1 will continue study of CorA and its mechanism of Mg2+ transport using site directed mutagenesis and transport assays to probe the hypothesized mechanism of transport and gating. Aim2 will continue structural work on the T. maritima CorA including determination of an open pore form of CorA and to determine the structure of the soluble domain of S. Typhimurium CorA. Aim 3 will focus on other members of the large CorA family. Bacterial ZntB has modest sequence identity to CorA but mediates efflux of Zn2+ rather than influx of Mg2+. Eukaryotic Mrs2 proteins mediate Mg2+ influx into mitochondria but have sequence similarity with CorA only in the membrane domain. We propose to test the hypothesis that the structures of ZntB and Mrs2 are identical to that of the CorA Mg2+ transporter by determining the crystal structures of the soluble domains of both transporters. Health relevance. Study of CorA is important because it is a virulence factor in prokaryotes and thus an antibiotic target, In addition, it mediate Mg2+ flux into mitochondria and thus is important in control of Mg2+ homeostasis in eukaryotic cells and possibly in the mitochondrion's role in apoptosis.

MG化学在生物阳离子中是独一无二的，细胞具有新颖的机制调节MG2+并促进其通过膜的通道。该提议着重于Cora MG2+转运蛋白，用于大多数Eubacteria和古细菌的主要MG2+摄取系统。水晶来自Thermotoga海事的Cora结构已确定为3.9分辨率。是一个带有两个跨膜（TM）螺旋的漏斗形同源物。细胞外区域是仅由连接两个TM螺旋的短循环组成。该通道组成在五个螺旋中，每个单体都有一个，并且看起来是由笨重的疏水侧链走了孔内的残留物。这些螺旋通过细胞质延伸到膜之外域，形成漏斗内表面。在漏斗外，孔的细胞质颈被高度保守的带电残留物包围。两个负电荷的螺旋在细胞质结构域中正电荷。这些外部螺旋可以用来抵消带正电荷的环，表明门控机制。明显的Mg2+离子在单体之间的细胞质结构域中结合，将扩展的螺旋从一个单体连接到另一个单体的一组螺旋。 MG2+绑定位点，在Cora直系同源物中保守，可以将开口孔与Mg2+的细胞内浓度联系起来。 AIM 1将继续研究Cora及其MG2+运输机制，使用定向地点诱变和运输测定法以探测运输和门控的假设机制。 AIM2将继续在T. Maritima Cora上进行结构性工作，包括确定开放孔 Cora的形式，并确定鼠伤寒链球菌的可溶性结构域的结构。 AIM 3将专注于大型Cora家族的其他成员。细菌ZNTB具有适度的序列对Cora的身份，但介导了Zn2+的外排，而不是Mg2+的流入。真核MRS2蛋白介导 Mg2+流入线粒体，但与CORA仅在膜结构域中具有序列相似性。我们提议检验Zntb和MRS2的结构与Cora Mg2+相同的假设通过确定两个转运蛋白可溶性结构域的晶体结构来转运蛋白。健康相关性。 Cora研究很重要，因为它是原核生物中的毒力因素，因此是另外，抗生素靶标将Mg2+通量介导到线粒体中，因此对于控制很重要真核细胞中的MG2+稳态，可能在线粒体中的作用。