Methanogenesis by Methanosarcina acetivorans involves two structurally and functionally distinct classes of heterodisulfide reductase
Methanogenesis by Methanosarcina acetivorans involves two structurally and functionally distinct classes of heterodisulfide reductase
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DOI：
10.1111/j.1365-2958.2009.06990.x
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发表时间：
2010-02-01
影响因子：
3.6
通讯作者：
Metcalf, William W.
中科院分区：
文献类型：
--
作者：
Buan, Nicole R.;Metcalf, William W.
P>生化研究揭示了两种不同类别的辅酶 B-辅酶 M 异二硫键 (CoB-S-S-CoM) 还原酶 (Hdr)，这是产甲烷古菌无氧呼吸所需的关键酶。细胞质 HdrABC 酶复合物存在于大多数产甲烷菌中，而膜结合的 HdrED 复合物仅存在于甲烷八叠目成员中。出乎意料的是，基因组数据表明在所有已测序的甲烷八叠球菌目基因组中都发现了两个 Hdr 类别的多个拷贝。乙酰甲烷八叠球菌 hdrED1 操纵子是组成型表达的，并且是在所有检查的生长条件下生存所需的，与 HdrED 作为主要 Hdr 一致。基于 hdrA1C1B1 突变体在甲基营养底物上的生长和产甲烷速率降低以及在乙酸盐上生长期间基因的下调，HdrABC 似乎专门参与甲基营养产甲烷作用。系统发育分析进一步支持了这一结论，系统发育分析表明生物体中 hdrA1 的存在与甲基营养型产甲烷基因的存在特定相关。对甲醇生长的 Delta hdrA1C1B1 菌株相对于野生型的 mRNA 丰度进行检查，发现合成（二）甲硫醚以及 CoB-SH 和 CoM-SH 的运输和生物合成所需的基因上调，表明该突变体在从铁氧还蛋白到 CoB-S-S-CoM 的电子转移中存在缺陷，从而导致辅因子限制。
P>Biochemical studies have revealed two distinct classes of Coenzyme B-Coenzyme M heterodisulfide (CoB-S-S-CoM) reductase (Hdr), a key enzyme required for anaerobic respiration in methane-producing archaea. A cytoplasmic HdrABC enzyme complex is found in most methanogens, whereas a membrane-bound HdrED complex is found exclusively in members of the order Methanosarcinales. Unexpectedly, genomic data indicate that multiple copies of both Hdr classes are found in all sequenced Methanosarcinales genomes. The Methanosarcina acetivorans hdrED1 operon is constitutively expressed and required for viability under all growth conditions examined, consistent with HdrED being the primary Hdr. HdrABC appears to be specifically involved in methylotrophic methanogenesis, based on reduced growth and methanogenesis rates of an hdrA1C1B1 mutant on methylotrophic substrates and downregulation of the genes during growth on acetate. This conclusion is further supported by phylogenetic analysis showing that the presence of hdrA1 in an organism is specifically correlated with the presence of genes for methylotrophic methanogenesis. Examination of mRNA abundance in methanol-grown Delta hdrA1C1B1 strains relative to wild-type revealed upregulation of genes required for synthesis of (di)methylsulfide and for transport and biosynthesis of CoB-SH and CoM-SH, suggesting that the mutant has a defect in electron transfer from ferredoxin to CoB-S-S-CoM that causes cofactor limitation.