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MECHANISM OF AUTOTROPHIC GROWTH WITH CO OR CO2 & H2

CO 或 CO2 自养生长机制

基本信息

批准号：
3272655
负责人：
Ganesh K Kumar
金额：
$ 5.18万
依托单位：
CASE WESTERN RESERVE UNIVERSITY
依托单位国家：
美国
项目类别：
财政年份：
1978
资助国家：
美国
起止时间：
1978-04-01 至 1994-06-30
项目状态：
已结题

项目摘要

These investigations have as the ultimate objective elucidation of the pathway by which certain bacteria grow with CO or CO2 and H2 as the source of carbon and energy. This is a pathway of autotrophic growth which differs from any previously described. It involves reduction of CO2 to methyltetrahydrofolate, then combination of this methyl group with CO and CoASH to form acetyl-CoA which is then used as the source of carbon for anabolic growth. The synthesis of acetyl-CoA from methyltetrahydrofolate, CO and CoASH is the unique portion of this pathway. Homogeneous proteins have been isolated from Clostridium thermoaceticum which catalyze this synthesis. They are CO dehydrogenase methyltransferase, a corrinoid enzyme, ferredoxin, and disulfide reductase. The CO dehydrogenase is the master enzyme of this pathway. It forms the Cl intermediate from CO or CO2 that is the precursor of the carbonyl group of acetyl-CoA, is the acceptor of the methyl from the methyl corrinoid enzyme and through the action of the CO dehydrogenase reductase combines with CoA. It then catalyzes the condensation of these three groups to acetyl-CoA. Our main objective is to elucidate how CO dehydrogenase catalyzes this condensation. We will use electron spin resonance (ESR), electron-nuclear double resonance, Mossbauer, and magnetic circular dichroism techniques to characterize the geometry and redox state of the Ni-Fe-S center of the CO dehydrogenase. We will investigate the mechanism of transfer of the methyl group from the methylated corrinoid protein to CO dehydrogenase with formation of an acetyl intermediate. We hope to detect this methyl-CO dehydrogenase complex using ESR techniques and chemically identify the amino acid sequence at the binding site. Likewise, the sequence near the linkage of CoASH to the enzyme, presumed to be by a disulfide bond, will be investigated. The monomers of the Alpha3Beta3 enzyme will be isolated, their metal content determined and genes for these proteins will be cloned and sequenced. The properties of CO dehydrogenase from certain methanogenic bacteria will be tested for their ability to synthesize acetyl-CoA to determine whether they may use a pathway of acetyl-CoA synthesis similar to that of C. thermoaceticum.

这些调查的最终目的是阐明某些细菌以CO或CO2和H2为源生长的途径碳和能源。这是一条自养生长的途径，不同于任何先前描述的。它包括减少二氧化碳，甲基四氢叶酸，然后将该甲基与CO和 CoASH形成乙酰辅酶A，然后将其用作碳源，合成代谢生长从甲基四氢叶酸合成乙酰辅酶A， CO和CoASH是该途径的独特部分。同质蛋白质已经从热乙酸梭菌中分离出来，合成. 它们是CO脱氢酶甲基转移酶，酶、铁氧还蛋白和二硫化物还原酶。 CO脱氢酶是这条通路的主要酶。它由CO或CO2形成Cl中间体是乙酰辅酶A羰基的前体，是受体来自甲基可啉酶的甲基，并通过 CO脱氢酶还原酶与CoA结合。然后催化将这三个基团缩合为乙酰辅酶A。我们的主要目标是阐明CO脱氢酶如何催化这种缩合。我们将使用电子自旋共振（ESR），电子-核双共振，穆斯堡尔和磁性圆二色性技术来表征 CO脱氢酶的Ni-Fe-S中心的几何形状和氧化还原状态。我们将研究甲基基团从甲基化的corrinoid蛋白转化为CO脱氢酶，乙酰基中间体我们希望能检测到这种甲基-CO脱氢酶复合物使用ESR技术和化学鉴定的氨基酸在结合位点的序列。同样，在连接附近的序列 CoASH的酶，推测是通过二硫键，将研究了将分离α 3 β 3酶的单体，它们的金属含量将被确定，这些蛋白质的基因将被克隆和序列测定研究了几种来源的CO脱氢酶的性质，将测试产甲烷细菌的合成能力，乙酰辅酶A，以确定他们是否可以使用乙酰辅酶A的途径与C.热醋酸。