Department of Molecular and Cell Biology, University of California, Berkeley, CA, USA.
Department of Chemistry, Boston University, Boston, MA, USA.
Nat Commun. 2024 Apr 17;15(1):3300. doi: 10.1038/s41467-024-47564-2.
Methanogens are a diverse group of Archaea that obligately couple energy conservation to the production of methane. Some methanogens encode alternate pathways for energy conservation, like anaerobic respiration, but the biochemical details of this process are unknown. We show that a multiheme c-type cytochrome called MmcA from Methanosarcina acetivorans is important for intracellular electron transport during methanogenesis and can also reduce extracellular electron acceptors like soluble Fe and anthraquinone-2,6-disulfonate. Consistent with these observations, MmcA displays reversible redox features ranging from -100 to -450 mV versus SHE. Additionally, mutants lacking mmcA have significantly slower Fe reduction rates. The mmcA locus is prevalent in members of the Order Methanosarcinales and is a part of a distinct clade of multiheme cytochromes that are closely related to octaheme tetrathionate reductases. Taken together, MmcA might act as an electron conduit that can potentially support a variety of energy conservation strategies that extend beyond methanogenesis.
产甲烷菌是古菌的一个多样化群体，它们必须将能量守恒与甲烷的产生联系起来。一些产甲烷菌编码了替代的能量守恒途径，如无氧呼吸，但这个过程的生化细节尚不清楚。我们表明，一种来自 Methanosarcina acetivorans 的多血红素 c 型细胞色素称为 MmcA，对于产甲烷过程中的细胞内电子传递很重要，并且可以还原细胞外电子受体，如可溶性 Fe 和蒽醌-2,6-二磺酸盐。这些观察结果一致表明，MmcA 显示出从 -100 到 -450 mV 相对于 SHE 的可逆氧化还原特征。此外，缺乏 mmcA 的突变体的 Fe 还原速率明显较慢。mmcA 基因座在 Methanosarcinales 目成员中很普遍，是与八血红素四硫代盐还原酶密切相关的多血红素细胞色素的一个独特分支的一部分。综上所述，MmcA 可能充当电子导管，能够支持超越产甲烷作用的多种能量守恒策略。
