One-megadalton metalloenzyme complex in Geobacter metallireducens involved in benzene ring reduction beyond the biological redox window
One-megadalton metalloenzyme complex in Geobacter metallireducens involved in benzene ring reduction beyond the biological redox window
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DOI：
10.1073/pnas.1819636116
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发表时间：
2019-02-05
影响因子：
11.1
通讯作者：
Boll, Matthias
中科院分区：
文献类型：
--
作者：
Huwiler, Simona G.;Loffler, Claudia;Boll, Matthias
可逆生物电子转移通常发生在标准氧化还原电位范围为 +0.8 至 -0.5 V 的氧化还原电对之间。脱芳香苯甲酰辅酶 A 还原酶 (BCR) 是缺氧位点芳香族化合物全球相关微生物降解的关键酶，可催化生物 Birch 还原超出该氧化还原窗口的负极限。 II 类 BCR 的结构特征 BamBC 亚基可在活性位点钨辅助因子处完成苯环还原；然而，吸能苯环还原的能量耦合所涉及的机制和成分仍然是假设的。我们提出了一种来自厌氧细菌金属还原地杆菌的 1-MDa 膜相关 Bam[(BC) 2DEFGHI] 2 复合物，含有 4 个钨、4 个锌、2 个硒代半胱氨酸、6 个 FAD 和 > 50 个 FeS 辅因子。结果表明，II 类 BCR 催化电子转移到芳香环，通过两个基于黄素的电子分叉事件产生环状 1,5-二烯酰基-CoA。这项工作通过高分子质量电子分叉机制扩展了我们对生物学中能量耦合的了解。
Reversible biological electron transfer usually occurs between redox couples at standard redox potentials ranging from +0.8 to -0.5 V. Dearomatizing benzoyl-CoA reductases (BCRs), key enzymes of the globally relevant microbial degradation of aromatic compounds at anoxic sites, catalyze a biological Birch reduction beyond the negative limit of this redox window. The structurally characterized BamBC subunits of class II BCRs accomplish benzene ring reduction at an active-site tungsten cofactor; however, the mechanism and components involved in the energetic coupling of endergonic benzene ring reduction have remained hypothetical. We present a 1-MDa, membrane-associated, Bam[(BC) 2DEFGHI] 2 complex from the anaerobic bacterium Geobacter metallireducens harboring 4 tungsten, 4 zinc, 2 selenocysteines, 6 FAD, and >50 FeS cofactors. The results suggest that class II BCRs catalyze electron transfer to the aromatic ring, yielding a cyclic 1,5-dienoyl-CoA via two flavin-based electron bifurcation events. This work expands our knowledge of energetic couplings in biology by high-molecular-mass electron bifurcating machineries.