Magnesium Homeostasis in Microorganisms

微生物中的镁稳态

• 批准号: 7647280
• 负责人: MICHAEL E MAGUIRE
• 金额: $ 34.2万
• 依托单位: CASE WESTERN RESERVE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 1991
• 资助国家: 美国
• 起止时间: 1991-01-01 至 2011-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7647280
• 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 maritima; Transmembrane Domain; Virulence; Virulence Factors; Work; attenuation; base; extracellular; insight; member; microorganism; monomer; novel; periplasm; research study; uptake

DESCRIPTION (provided by applicant): Mg2+ chemistry is unique among biological cations, and cells possess novel mechanisms for regulating Mg2+ and facilitating its passage through membranes. This application focuses on the CorA Mg2+ transporter, the primary Mg2+ uptake system for most Eubacteria and Archaea. The crystal structure of CorA from Thermotoga maritima has been determined to 3.9 A resolution. It is a funnel-shaped homopentamer with 2 transmembrane (TM) helices. The extracellular region is composed of only a short conserved loop that connects the 2 TM helices. The channel is composed of 5 helices, 1 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. 2 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 1 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. Aim 2 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 mediates 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.

描述（由申请人提供）：MG2+化学在生物阳离子中是独一无二的，并且细胞具有调节MG2+并促进其通过膜的新机制。该应用的重点是Cora MG2+转运蛋白，这是大多数Eubacteria和古细菌的主要MG2+摄取系统。来自Thermotoga Maritima的Cora的晶体结构已确定为3.9分辨率。它是漏斗形的同型同源物，具有2个跨膜（TM）螺旋。细胞外区域仅由连接2 TM螺旋的短循环组成。该通道由5个螺旋组成，每种单体1个螺旋组成，并由孔内笨重的疏水残基的侧链盖住。这些螺旋通过细胞质结构域延伸到膜之外，形成漏斗内表面。在漏斗之外，孔的细胞质颈部被高度保守的带正电荷残基的环包围。 2个细胞质结构域中带负电荷的螺旋向后延伸到漏斗外的膜，并固定正电荷环。这些外部螺旋可以用来抵消带正电荷的环，提示门控机制。单体之间的细胞质结构域结合了明显的Mg2+离子，将延伸的螺旋从1个单体连接到另一个单体的一组螺旋。在Cora直系同源物中保守的MG2+结合位点可以将开口孔与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，使用定向诱变和转运测定法，以探测假设的运输和门控机制。 AIM 2将继续在Maritima Cora的T. Maritima Cora上进行结构性工作，包括确定Cora的开放孔形式，并确定鼠伤寒沙门氏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具有适度的序列身份，但介导Zn2+的外排，而不是Mg2+的流入。 真核MRS2蛋白介导Mg2+流入到线粒体中，但仅在膜结构域中与CORA具有相似性。我们建议通过确定两个转运蛋白可溶性结构域的晶体结构来检验Zntb和MRS2的结构与Cora MG2+转运蛋白相同的假设。健康相关性。 Cora的研究很重要，因为它是原核生物中的毒力因子，因此是抗生素靶标。此外，它将MG2+通量介导为线粒体，因此对于控制真核细胞中的MG2+稳态以及线粒体在凋亡中的作用中很重要。