Electron Transport in Archaeoglobus fulgidus

Hartzell领域的成员在极端环境中茁壮成长，包括热液和厌氧壁龛，这可能代表了生命起源时地球上的条件。 古生菌属的成员是唯一的硫酸盐还原菌，也是唯一的极端嗜热硫酸盐还原菌。 硫酸盐还原菌是严格的厌氧微生物，其利用硫酸盐作为异化硫酸盐还原的末端电子受体来产生质子动力。 该项目使用生物化学和微生物遗传学方法相结合，以了解闪烁古生菌如何利用D-乳酸作为生长的唯一碳源和将硫酸盐还原为硫化氢的电子。 A.闪电鱼基因组包括一个单一的基因dld，预测编码D-乳酸脱氢酶，膜相关酶，氧化D-乳酸为丙酮酸和转移电子到厌氧呼吸链。 dld基因是5个A. fulgidus基因可能包含操纵子，这将通过绘制dld mRNA的起始位点直接进行测试。 其上游（noxA 2; NADH氧化酶）和下游（abc，ABC转运蛋白）基因也可能编码参与D-乳酸催化的产物。 编码Dld和NoxA 2的基因已在E.杆菌 从E.大肠杆菌，是热稳定的，并具有D-乳酸特异性脱氢酶活性。 纯化的NoxA 2也是稳定的，需要NAD才能有活性。 纯化的Dld和NoxA 2将进行生物化学表征，以鉴定可能参与电子转移的辅因子和金属。 遗传技术将被用来确定这些酶的关键氨基酸残基参与辅因子结合和氧化还原循环。 为了确定Dld和NoxA 2是否相互作用形成复合物，并鉴定与Dld相互作用的其他蛋白质，将使用亲和色谱法和酵母双杂交方法。 A. fulgidus是第一个有完整基因组序列的硫酸盐还原剂。 从这一序列出发，生物化学和遗传学的方法将提供强有力的工具来重建其不寻常的电子流呼吸途径，起始于D-lactate.硫酸盐还原生物通过降解和解毒沉积物和沃茨中的化合物在环境中发挥着关键作用。用于消除这些化合物的细胞组分是在生长期间为硫酸盐还原剂进行能量生产的相同蛋白质。 与包括哺乳动物在内的生物体不同，它们在能量产生过程中使用O2作为电子汇，硫酸盐还原剂使用SO 4作为电子汇。 该项目的目的是确定参与硫酸盐还原剂（Archaeoglobus fulgidus）能量生产的蛋白质，并确定这些蛋白质如何相互作用以允许电子流向硫酸盐。 A.闪电藻是一种古老的微生物，它只能在非常高的温度下生长（83 ℃，181 ℉）。 该项目最初将侧重于乳酸脱氢酶和NADH氧化酶两种蛋白质的活性和性质。 这些蛋白质与其他单细胞生物体以及包括人类在内的复杂生物体的能量生产相关。 通过这项研究获得的信息将帮助科学家了解哪些蛋白质参与了能量产生的基本过程，以及这些蛋白质如何相互连接以控制这个普遍的复杂过程。

HartzellMembers of the domain Archaea thrive in extreme environments, including hydrothermal and anaerobic niches, that may represent the conditions on the earth when life originated. Members of the genus Archaeoglobus are the only sulfate reducers in the Archaea and the only hyperthermophilic sulfate-reducers. Sulfate-reducers are strict anaerobes that use sulfate as the terminal electron acceptor of dissimilatory sulfate reduction to generate a proton motive force. This project uses a combination of biochemical and microbial genetic approaches to understand how Archaeoglobus fulgidus utilizes D-lactate as a sole source of carbon for growth and electrons for reduction of sulfate to hydrogen sulfide. The sequence of the A. fulgidus genome includes a single gene, dld, predicted to encode D-lactate dehydrogenase, the membrane-associated enzyme that oxidizes D-lactate to pyruvate and transfers electrons to the anaerobic respiratory chain. The dld gene is the central gene of five A. fulgidus genes that likely comprise an operon, which will be tested directly by mapping the start site of the dld mRNA. Its upstream (noxA2; NADH oxidase) and downstream (abc, ABC transporter) genes may also encode products involved in D-lactate catabolism. The genes encoding Dld and NoxA2 have been expressed in E. coli. Dld, purified from E. coli, is thermostable and has D-lactate -specific dehydrogenase activity. Purified NoxA2 also is stable and requires NAD for activity. Purified Dld and NoxA2 will be characterized biochemically to identify cofactors and metals that may be involved in electron transfer. Genetic techniques will be used to identify the critical amino acid residues of these enzymes that are involved in cofactor binding and oxidation-reduction cycles. To determine if Dld and NoxA2 interact to form a complex, and to identify other proteins that interact with Dld, affinity chromatography and the yeast two-hybrid approach will be used. A. fulgidus is the first sulfate reducer for which a complete genome sequence is available. Starting from this sequence, biochemical and genetic approaches will provide powerful tools to reconstitute its unusual respiratory pathway of electron flow that initiates with D-lactate.Sulfate-reducing organisms play critical roles in the environment by degrading and detoxifying compounds in sediments and waters. The cellular components used to eliminate these compounds are the same proteins that carry out energy production for the sulfate-reducer during growth. Unlike organisms, including mammals, which use O2 as a sink for electrons during energy production, sulfate-reducers use SO4 as a sink for electrons. This project is aimed at identifying the proteins that are involved in energy production in the sulfate-reducer, Archaeoglobus fulgidus and determining how these proteins interact with one another to permit the flow of electrons to sulfate. A. fulgidus, a member of an ancient group of microbes, grows only at very high temperatures (83 C, 181 F). The project will focus initially on the activity and properties of two proteins, lactate dehydrogenase and NADH oxidase. These proteins are related to proteins involved in energy production from other single-cells organisms as well as complex organisms, including humans. The information obtained through this research will help scientists understand which proteins are involved the essential process of energy production and how these proteins link to one another to control this universal, complex process.