Methylcobalamin:Coenzyme M Methyltransferase Isoenzymes MtaA and MtbA from Methanosarcina barkeri. Cloning, Sequencing and Differential Transcription of the Encoding Genes, and Functional Overexpression of the mtaA Gene in Escherichia coli
摘要:
Methanosarcina barkeri 中已知含有两种甲基转移酶同工酶,分别命名为 MtaA 和 MtbA,它们能够催化甲基辅酶 M 从甲基钴胺素和辅酶 M 的形成。编码这两个可溶性 34 kDa 蛋白的基因已被克隆和测序。 mtaA 和 mtbA 在基因组的不同区域被发现,每个基因各自形成一个单顺反子转录单位。Northern 印迹分析显示,当 M. barkeri 在甲醇上生长时, mtaA 的转录优先发生;而当该菌在 H2/CO2 或三甲胺上生长时, mtbA 基因被转录。通过推导的氨基酸序列比较发现,这两种同工酶的序列相似度为 37%。两种同工酶的序列均与 Escherichia coli 的尿卟啉原 III 脱羧酶表现出相似性。 mtaA 基因被一个编码六个组氨酸的序列标记,该序列位于 mtaA 启动子上游 6 个碱基对处,随后在 E. coli 中实现了该基因的功能性过表达。研究发现, E. coli 表达的蛋白质中有 25% 具有活性甲基转移酶功能,通过两步纯化可获得近乎纯度的蛋白质,产率达到 70%。
Binding of Coenzyme B Induces a Major Conformational Change in the Active Site of Methyl-Coenzyme M Reductase
作者:Sieglinde Ebner、Bernhard Jaun、Meike Goenrich、Rudolf K. Thauer、Jeffrey Harmer
DOI:10.1021/ja906367h
日期:2010.1.20
Methyl-coenzyme M reductase (MCR) is the key enzyme in methane formation by methanogenic Archaea. It converts the thioether methyl-coenzyme M and the thiol coenzyme B into methane and the heterodisulfide of coenzyme M and coenzyme B. The catalytic mechanism of MCR and the role of its prosthetic group, the nickel hydrocorphin coenzyme F(430), is still disputed, and no intermediates have been observed
甲基辅酶 M 还原酶 (MCR) 是产甲烷古细菌形成甲烷的关键酶。它将硫醚甲基辅酶 M 和硫醇辅酶 B 转化为甲烷和辅酶 M 和辅酶 B 的杂二硫化物。 MCR 的催化机制及其辅基镍氢卟啉辅酶 F(430) 的作用仍存在争议,并且当酶与天然底物一起温育时,迄今为止通过快速光谱技术还没有观察到中间体。在竞争性抑制剂辅酶 M 代替甲基辅酶 M 存在的情况下,将辅酶 B 添加到活性 Ni(I) 状态 MCR(red1) 诱导两个新物种,称为 MCR(red2a) 和 MCR(red2r),它们已被表征通过脉冲 EPR 光谱。在这里,我们表明辅酶 B 的 S-甲基-和 S-三氟甲基类似物也可以诱导两个 MCR(red2) 信号。 MCR(red2a) 和 MCR(red2r) 诱导的 (19)F-ENDOR 数据S-CF(3)-辅酶 B 表明,与辅酶 B 类似物结合后,辅酶 B 的 7-硫代庚酰基链的末端向
Intermediates in the Catalytic Cycle of Methyl Coenzyme M Reductase: Isotope Exchange is Consistent with Formation of a σ-Alkane-Nickel Complex
作者:Silvan Scheller、Meike Goenrich、Stefan Mayr、Rudolf K. Thauer、Bernhard Jaun
DOI:10.1002/anie.201003214
日期:2010.10.25
catalyzes the formation of CH3D and CH2D2 in a deuterated medium. CH2D2 is formed by an exchange of deuterium into the S‐methyl group of the substrate. Deuterium is incorporated at both carbon atoms of the S‐ethyl group of ethyl coenzymeM, and a 13C label is rapidly scrambled within the ethyl group (see scheme). Thus, at least one intermediate is formed and the isotopeexchange pattern is consistent with formation
甲烷生成的关键镍酶(MCR)催化氘化介质中CH 3 D和CH 2 D 2的形成。CH 2 D 2是通过将氘交换为底物的S-甲基而形成的。氘结合在乙基辅酶M的S-乙基的两个碳原子上,并且13 C标记在乙基内快速加乱(请参见方案)。因此,形成了至少一种中间体,并且同位素交换模式与σ-烷烃-镍络合物的形成相一致。
Methane Formation by Reaction of a Methyl Thioether with a Photo-Excited Nickel Thiolate—A Process Mimicking Methanogenesis in Archaea
The formation of a sulfuranyl radical intermediate followed by methyl transfer to the nickel(I) center of coenzyme F430 and generation of the disulfide has been proposed as a possible mechanism for the formation of methane catalyzed by methylcoenzymeMreductase in methanogenic archaea. In order to test this hypothesis, a sterically shielded, bifunctional model substrate that contained a methyl thioether
Spectroscopic and Kinetic Studies of the Reaction of Bromopropanesulfonate with Methyl-coenzyme M Reductase
作者:Ryan C. Kunz、Yih-Chern Horng、Stephen W. Ragsdale
DOI:10.1074/jbc.m606715200
日期:2006.11
Methyl-coenzyme Mreductase (MCR) catalyzes the final step of methanogenesis in which coenzyme B and methyl-coenzyme M are converted to methane and the heterodisulfide, CoMS-SCoB. MCR also appears to initiate anaerobic methane oxidation (reverse methanogenesis). At the active site of MCR is coenzyme F, a nickel tetrapyrrole. This paper describes the reaction of the active MCR state with the potent
Post-translational modifications in the active site region of methyl-coenzyme M reductase from methanogenic and methanotrophic archaea
作者:Jörg Kahnt、Bärbel Buchenau、Felix Mahlert、Martin Krüger、Seigo Shima、Rudolf K. Thauer
DOI:10.1111/j.1742-4658.2007.06016.x
日期:2007.9
methylations. The MS analysis included MCR I and MCR II from Methanothermobacter marburgensis, MCR I from Methanocaldococcus jannaschii and Methanoculleus thermophilus, and MCR from Methanococcus voltae, Methanopyrus kandleri and Methanosarcinabarkeri. Two MCRs isolated from Black Sea mats containing mainly methanotrophic archaea of the ANME‐1 cluster were also analyzed.