MECHANISMS OF ME-TRANSFER AND ACETYL-COA SYNTHESIS

产甲烷细菌是人类肠道菌群的重要组成部分，其存在和/或缺失已被证明具有独特的流行病学。因此，对产甲烷菌代谢途径的理解与人类健康有着意想不到的相关性。目的是阐明参与甲烷菌基本甲基转移反应的多亚基配合物的结构。这些配合物中较大的乙酰辅酶a脱碳酶合成酶（ACDS）介导醋酸酯的C-C键裂解。该复合物被划分为三个独立的组分，每个组分催化三种反应中的一种：可逆乙酰辅酶a转移酶活性、CO:CO2氧化还原酶活性和甲基转移酶活性。长期目标是确定这些成分的结构，以便深入了解它们的催化机制。一旦获得所有这些结构，它们将被用来组装ACDS复合物的完整图像，可以作为理解不同组分之间底物转移机制的框架。第二个目标是针对从甲胺中参与甲基营养生长的蛋白质的结构测定。这里的主要焦点不仅在于阐明甲基转移酶及其同源类蛋白的结构，而且还在于了解甲基是如何转移到类蛋白因子和从类蛋白因子转移的。由于这些类冠状细胞中心在生物学中无处不在，因此这些见解将与许多生物系统普遍相关。

Methanogenic bacteria form an important part of the human intestinal flora where their presence and/or absence has been shown to have a distinct epidemiology. Hence the understanding of the metabolic pathways of methanogenes has unexpected relevance to human health. The objective of this proposal is to elucidate the structures of multi- subunit complexes that participate in fundamental methyl transfer reactions in methanogens. The larger of these complexes, the acetyl-CoA decarbonylase synthase (ACDS), mediates the C-C bond cleavage of acetate. This complex is compartmentalized into three discrete components, each of which catalyzes one of three reactions: reversible acetyl-CoA transferase activity, CO:CO2 oxidoreductase activity, and methyltransferase activity. The long-term goal is to determine the structures of each of these components in order to gain insight into their catalytic mechanisms. Once all of these structures are obtained, they will be utilized to assemble a complete picture of the ACDS complex that can serve as a framework for understanding the mechanisms of substrate transfer between the different components. The second target is directed at the structural determination of proteins involved in methylotrophic growth from methylamines. Here too the major focus is not only in elucidating the structures of a methyl transferase and its cognate corrinoid protein, but also to understand how a methyl group is transferred to and from a corrinoid factor. As these corrinoid centers are ubiquitous in biology, such insights will be of general relevance to many biological systems.