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首页> 外文期刊>Biochemistry >Pivotal Roles of Three Conserved Carboxyl Residues of the NuoC (30k) Segment in the Structural Integrity of Proton-Translocating NADH-Quinone Oxidoreductase from Escherichia coli
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Pivotal Roles of Three Conserved Carboxyl Residues of the NuoC (30k) Segment in the Structural Integrity of Proton-Translocating NADH-Quinone Oxidoreductase from Escherichia coli

机译：NuoC（30k）节段的三个保守的羧基残基在质子转移质子的NADH-奎宁氧化还原酶的结构完整性中的关键作用

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摘要

The prokaryotic proton-translocating NADH-quinone oxidoreductase (NDH-1) is an L-shapednmembrane-bound enzyme that contains 14 subunits (NuoA-NuoN or Nqo1-Nqo14). All subunits haventheir counterparts in the eukaryotic enzyme (complex I). NDH-1 consists of two domains: the peripheral armn(NuoB, -C, -D, -E, -F, -G, and -I) and the membrane arm (NuoA, -H, -J, -K, -L, -M, and -N). In Escherichiancoli NDH-1, the hydrophilic subunits NuoC/Nqo5/30k and NuoD/Nqo4/49k are fused together in a singlenpolypeptide as the NuoCD subunit. The NuoCD subunit is the only subunit that does not bear a cofactor innthe peripheral arm.While some roles for inhibitor and quinone association have been reported for the NuoDnsegment, structural and functional roles of the NuoC segment remain mostly elusive. In this work, 14 highlynconserved residues of the NuoC segment were mutated and 21 mutants were constructed using thenchromosomal gene manipulation technique. From the enzymatic assays and immunochemical and blue-nnative gel analyses, it was found that residues Glu-138, Glu-140, and Asp-143 that are thought to be in thenthird R-helix are absolutely required for the energy-transducing NDH-1 activities and the assembly of thenwhole enzyme. Together with available information for the hydrophobic subunits, we propose that Glu-138,nGlu-140, and Asp-143 of the NuoC segment may have a pivotal role in the structural stability of NDH-1.
机译：原核质子转运NADH-醌氧化还原酶（NDH-1）是一个L形的膜结合酶，包含14个亚基（NuoA-NuoN或Nqo1-Nqo14）。所有亚基在真核酶中都具有对应物（复合体I）。 NDH-1由两个域组成：外围臂（NuoB，-C，-D，-E，-F，-G和-I）和膜臂（NuoA，-H，-J，-K，- L，-M和-N）。在大肠埃希氏大肠杆菌NDH-1中，亲水性亚基NuoC / Nqo5 / 30k和NuoD / Nqo4 / 49k在单肽中融合在一起，作为NuoCD亚基。 NuoCD亚基是唯一在外周臂中不带有辅因子的亚基。虽然据报道，NuoDnsegment具有抑制剂和醌键的某些作用，但大部分的NuoC段的结构和功能作用仍然难以捉摸。在这项工作中，NuoC区段的14个高度保守的残基发生了突变，并使用染色体基因操作技术构建了21个突变体。从酶促分析，免疫化学和蓝色变性凝胶分析中发现，能量转化NDH-绝对需要被认为存在于第三R-螺旋中的残基Glu-138，Glu-140和Asp-143。 1活动和整个酶的组装。连同疏水亚基的可用信息，我们建议，NuoC段的Glu-138，nGlu-140和Asp-143可能在NDH-1的结构稳定性中起关键作用。

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