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首页> 外文期刊>MicrobiologyOpen >Exploring the directionality of Escherichia coli formate hydrogenlyase: a membrane-bound enzyme capable of fixing carbon dioxide to organic acid
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Exploring the directionality of Escherichia coli formate hydrogenlyase: a membrane-bound enzyme capable of fixing carbon dioxide to organic acid

机译：探索大肠杆菌甲酸氢水解酶的方向性：一种能够将二氧化碳固定为有机酸的膜结合酶

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Abstract During mixed-acid fermentation Escherichia coli produces formate, which is initially excreted out the cell. Accumulation of formate, and dropping extracellular pH, leads to biosynthesis of the formate hydrogenlyase (FHL) complex. FHL consists of membrane and soluble domains anchored within the inner membrane. The soluble domain comprises a [NiFe] hydrogenase and a formate dehydrogenase that link formate oxidation directly to proton reduction with the release of CO 2 and H 2 . Thus, the function of FHL is to oxidize excess formate at low pH. FHL subunits share identity with subunits of the respiratory Complex I. In particular, the FHL membrane domain contains subunits (HycC and HycD) that are homologs of NuoL/M/N and NuoH, respectively, which have been implicated in proton translocation. In this work, strain engineering and new assays demonstrate unequivocally the nonphysiological reverse activity of FHL in vivo and in vitro. Harnessing FHL to reduce CO 2 to formate is biotechnologically important. Moreover, assays for both possible FHL reactions provide opportunities to explore the bioenergetics using biochemical and genetic approaches. Comprehensive mutagenesis of hycC did not identify any single amino acid residues essential for FHL operation. However, the HycD E199, E201, and E203 residues were found to be critically important for FHL function.
机译：摘要混合酸发酵过程中，大肠杆菌产生甲酸盐，该甲酸盐最初从细胞中排出。甲酸盐的积累和细胞外pH的下降导致甲酸盐氢解酶（FHL）复合物的生物合成。 FHL由膜和锚定在内膜中的可溶性域组成。可溶性结构域包含[NiFe]氢化酶和甲酸脱氢酶，它们直接将甲酸氧化与质子还原联系起来，并释放CO 2和H 2。因此，FHL的功能是在低pH值下氧化过量的甲酸。 FHL亚基与呼吸复合体I的亚基共享同一性。特别是，FHL膜结构域包含分别与NuoL / M / N和NuoH同源的亚基（HycC和HycD），已与质子易位有关。在这项工作中，菌株工程和新的测定法明确地证明了FHL在体内和体外的非生理反向活性。利用FHL将CO 2还原成甲酸盐在生物技术上很重要。此外，对两种可能的FHL反应的测定均提供了使用生化和遗传方法探索生物能学的机会。 hycC的全面诱变未发现FHL操作必不可少的任何单个氨基酸残基。但是，发现HycD E199，E201和E203残基对FHL功能至关重要。

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