PDF(Pubmed)
Abstract：
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 Fe3+ 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 Fe3+ 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.
摘要：
产甲烷菌是古细菌的一个多样化的群体，它们必须将节能与甲烷的生产联系起来。一些产甲烷菌编码能量守恒的替代途径，比如无氧呼吸，但是这个过程的生化细节是未知的。我们表明，来自甲烷甲烷的多血红素c型细胞色素MmcA对于产甲烷过程中的细胞内电子传输很重要，并且还可以减少细胞外电子受体，例如可溶性Fe3和蒽醌-2,6-二磺酸盐。与这些观察结果一致，相对于SHE,MmcA显示范围从-100到-450mV的可逆氧化还原特征。此外,缺乏mmcA的突变体具有显著较慢的Fe3+还原速率。mmcA基因座在Methanosarcinales的成员中普遍存在，并且是与八血红素四硫氨酸还原酶密切相关的多血红素细胞色素的不同进化枝的一部分。一起来看,MmcA可能充当电子导管，可以潜在地支持各种超越产甲烷的节能策略。
