Coupling of ferredoxin and heterodisulfide reduction via electron bifurcation in hydrogenotrophic methanogenic archaea
Coupling of ferredoxin and heterodisulfide reduction via electron bifurcation in hydrogenotrophic methanogenic archaea
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DOI：
10.1073/pnas.1016761108
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发表时间：
2011-02-15
影响因子：
11.1
通讯作者：
Thauer, Rudolf K.
中科院分区：
文献类型：
--
作者：
Kaster, Anne-Kristin;Moll, Johanna;Thauer, Rudolf K.
在依靠 H-2 和 CO2 生长的产甲烷古菌中，产甲烷作用的第一步是铁氧还蛋白依赖性 CO2 与 H-2 的吸能还原为甲酰基甲烷呋喃，最后一步是异二硫键 CoM-S-S-CoB 与 H-2 的放能还原为辅酶 M (CoM-SH) 和辅酶 B (CoB-SH)。我们最近提出，在氢营养产甲烷菌中，这两个反应通过细胞质 MvhADG/HdrABC 复合物进行能量耦合。据报道，来自马尔堡产热甲烷杆菌的纯化复合物可催化铁氧还蛋白与 H-2 的 CoM-S-S-CoB 依赖性还原。添加每摩尔 CoM-S-S-CoB，减少 1 mol 铁氧还蛋白 (Fd)，表明电子分叉耦合机制：2H(2) + Fd(ox) + CoM-S-S-CoB -> Fd(red)(2-) + CoM-SH + CoB-SH + 2H(+)：这种耦合化学计量与从 4 H-2 和 CO2 获得的每摩尔甲烷 ATP 增益一致。 0.5 由 8 Pa 的 H-2 阈值浓度和高达 3 g/mol 甲烷的生长产率推导出来。
In methanogenic archaea growing on H-2 and CO2 the first step in methanogenesis is the ferredoxin-dependent endergonic reduction of CO2 with H-2 to formylmethanofuran and the last step is the exergonic reduction of the heterodisulfide CoM-S-S-CoB with H-2 to coenzyme M (CoM-SH) and coenzyme B (CoB-SH). We recently proposed that in hydrogenotrophic methanogens the two reactions are energetically coupled via the cytoplasmic MvhADG/HdrABC complex. It is reported here that the purified complex from Methanothermobacter marburgensis catalyzes the CoM-S-S-CoB-dependent reduction of ferredoxin with H-2. Per mole CoM-S-S-CoB added, 1 mol of ferredoxin (Fd) was reduced, indicating an electron bifurcation coupling mechanism: 2H(2) + Fd(ox) + CoM-S-S-CoB -> Fd(red)(2-) + CoM-SH + CoB-SH + 2H(+): This stoichiometry of coupling is consistent with an ATP gain per mole methane from 4 H-2 and CO2 of near 0.5 deduced from an H-2-threshold concentration of 8 Pa and a growth yield of up to 3 g/mol methane.