Leipzig University, Institute of Biochemistry, Brüderstraße 34, 04103, Leipzig, Germany.
Helmholtz Centre for Environmental Research - UFZ, Isotope Biogeochemistry, Permoserstraße 15, 04318, Leipzig, Germany.
Sci Rep. 2018 May 9;8(1):7404. doi: 10.1038/s41598-018-25716-x.
The biological formation of methane (methanogenesis) is a globally important process, which is exploited in biogas technology, but also contributes to global warming through the release of a potent greenhouse gas into the atmosphere. The last and methane-releasing step of methanogenesis is catalysed by the enzyme methyl-coenzyme M reductase (MCR), which carries several exceptional posttranslational amino acid modifications. Among these, a 5-C-(S)-methylarginine is located close to the active site of the enzyme. Here, we show that a unique Radical S-adenosyl-L-methionine (SAM) methyltransferase is required for the methylation of the arginine residue. The gene encoding the methyltransferase is currently annotated as "methanogenesis marker 10" whose function was unknown until now. The deletion of the methyltransferase gene ma4551 in Methanosarcina acetivorans WWM1 leads to the production of an active MCR lacking the C-5-methylation of the respective arginine residue. The growth behaviour of the corresponding M. acetivorans mutant strain and the biophysical characterization of the isolated MCR indicate that the methylated arginine is important for MCR stability under stress conditions.
甲烷（沼气生成）的生物形成是一个在全球范围内具有重要意义的过程，它被应用于沼气技术中，但也通过向大气中释放一种强力温室气体而导致全球变暖。沼气生成的最后一步也是释放甲烷的步骤由酶甲基辅酶 M 还原酶（MCR）催化，该酶具有几个特殊的翻译后氨基酸修饰。其中，靠近酶活性位点的位置有一个 5-C-（S）-甲基精氨酸。在这里，我们表明，一种独特的活性 S-腺苷甲硫氨酸（SAM）甲基转移酶对于精氨酸残基的甲基化是必需的。编码甲基转移酶的基因目前被注释为“沼气生成标记 10”，直到现在其功能还未知。在 Methanosarcina acetivorans WWM1 中删除甲基转移酶基因 ma4551 会导致产生一种缺少相应精氨酸 C-5 甲基化的活性 MCR。相应的 M. acetivorans 突变株的生长行为和分离的 MCR 的生物物理特性表明，在应激条件下，甲基化的精氨酸对于 MCR 的稳定性很重要。
