UNDERSTANDING THE MOLECULAR DETAILS OF BIOLOGICAL METHANE FORMATION

这个子项目是许多利用 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 厌氧产甲烷古菌（产甲烷菌）形成甲烷作为其代谢的最终产物。据估计，产甲烷菌每年产生约10亿吨甲烷。甲烷是一种潜在的温室气体，但也是一种潜在的有价值的可再生能源。这个吗？双刃剑？使生物甲烷生成的研究与我们当今世界面临的两个最关键的挑战相关。甲基辅酶M还原酶（MCR）存在于所有产甲烷菌中，催化生物甲烷生产的最后一步。以甲基辅酶M（methyl-SCoM，2-（methylthio）ethanesulfonate）和辅酶B（CoBSH，N-7-mercaptoheptanoyl threonyl phosphate）为底物，CoBSH为电子供体，甲基-SCoM发生2电子还原反应，生成甲烷和CoBS-SCoM混合二硫化物。MCR含有辅酶F430，一种氧化还原活性镍四氢可啡肽，是自然界中已知还原程度最高的四吡咯。辅酶F430的大还原电位意味着稳定酶的还原和活性形式用于结构研究已经被证明是不可能的。迄今为止，晶体学研究是用氧化的催化非活性形式进行的。在与Steve Ragsdale（密歇根大学医学院）的合作中，我们现在相信我们可以通过维持从微生物生长到晶体冷冻的厌氧条件，以约70%的单晶占有率产生酶的活性形式MCRred 1。有了这些晶体在手，大量的冷冻捕获中间体和抑制形式变得容易获得。晶体的高衍射质量（高达1.2埃分辨率）使我们能够了解这种极不寻常的酶的结构与功能之间的关系。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The anaerobic methanogenic archaea (methanogens) form methane as an end product of their metabolism. It has been estimated that methanogens produce approximately 1 billion tons of methane every year. Methane is a potent greenhouse gas, but also represents a potential valuable source of renewable energy. This ?double-edged sword? makes the study of biological methane generation of relevance to two of the most critical challenges we face in the World today. Found in all methanogens, methyl-coenzyme M reductase (MCR) catalyzes the final step in biological methane production. Methyl-coenzyme M (methyl-SCoM, 2-(methylthio)ethanesulfonate) and coenzyme B (CoBSH, N-7-mercaptoheptanoylthreonine phosphate) are the substrates for the reaction, in which CoBSH serves as the electron donor for the 2 electron reduction of methyl-SCoM to produce methane and a CoBS-SCoM mixed disulfide. MCR contains coenzyme F430, a redox active nickel tetrahydrocorphin that is the most reduced tetrapyrrole known in nature. The large reduction potential of coenzyme F430 means that stabilizing the reduced and active form of the enzyme for structural studies has proved impossible up to this point. Crystallographic studies thus far have been conducted with oxidized catalytically inactive forms. In collaboration with Steve Ragsdale (University of Michigan Medical School) we now believe we can generate the active form of the enzyme, MCRred1, at ~70% occupancy in single crystals through maintaining anaerobic conditions from microbe grow-up to crystal freezing. With these crystals in hand, a plethora of freeze trapped intermediates and inhibited forms become accessible. The high diffraction quality of the crystals (up to 1.2 Angstroms resolution) allows us to understand how structure relates to function in this highly unusual enzyme.