Genetic characterization of a single bifunctional enzyme for fumarate reduction and succinate oxidation in Geobacter sulfurreducens and engineering of fumarate reduction in Geobacter metallireducens
Genetic characterization of a single bifunctional enzyme for fumarate reduction and succinate oxidation in Geobacter sulfurreducens and engineering of fumarate reduction in Geobacter metallireducens
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DOI：
10.1128/jb.188.2.450-455.2006
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发表时间：
2006-01-01
影响因子：
3.2
通讯作者：
Lovley, DR
中科院分区：
文献类型：
--
作者：
Butler, JE;Glaven, RH;Lovley, DR
对硫还原地杆菌还原富马酸的机理进行了研究。该基因组含有富马酸异三聚体还原酶FrdCAB的编码基因，与产丁二酸狼疮杆菌的富马酸还原酶和枯草芽孢杆菌的琥珀酸脱氢酶具有同源性。该酶催化亚基的突变导致了一株缺乏富马酸还原酶活性的菌株，并且不能以富马酸作为末端电子受体生长。突变菌株也缺乏琥珀酸脱氢酶活性，不能以乙酸盐为电子供体，以Fe(111)为电子受体。突变菌株能够以乙酸盐为电子供体，以Fe(111)为电子受体，在三元酸循环中提供富马酸以减轻琥珀酸脱氢酶活性的需要。突变株在此条件下生长速度较快，细胞产量高于需要琥珀酸脱氢酶活力的野生型，说明琥珀酸脱氢酶反应耗能大。在金属还原地杆菌中存在一个同源的frdCAB操纵子，它不能在富马酸作为末端电子受体的情况下生长。当硫还原革兰氏菌的二元酸转运蛋白在金属还原革兰氏菌中表达时，富马酸作为唯一的电子受体生长成为可能。这些结果表明，与以前描述的生物不同，硫还原革兰氏菌和可能的金属革兰氏菌在体内使用相同的酶进行富马酸还原和琥珀酸氧化。
The mechanism of fumarate reduction in Geobacter sulfurreducens was investigated. The genome contained genes encoding a heterotrimeric fumarate reductase, FrdCAB, with homology to the fumarate reductase of Wolinella succinogenes and the succinate dehydrogenase of Bacillus subtilis. Mutation of the putative catalytic subunit of the enzyme resulted in a strain that lacked fumarate reductase activity and was unable to grow with fumarate as the terminal electron acceptor. The mutant strain also lacked succinate dehydrogenase activity and did not grow with acetate as the electron donor and Fe(111) as the electron acceptor. The mutant strain could grow with acetate as the electron donor and Fe(111) as the electron acceptor if fumarate was provided to alleviate the need for succinate dehydrogenase activity in the tricarboxylic acid cycle. The growth rate of the mutant strain under these conditions was faster and the cell yields were higher than for wild type grown under conditions requiring succinate dehydrogenase activity, suggesting that the succinate dehydrogenase reaction consumes energy. An orthologous frdCAB operon was present in Geobacter metallireducens, which cannot grow with fumarate as the terminal electron acceptor. When a putative dicarboxylic acid transporter from G. sulfurreducens was expressed in G. metallireducens, growth with fumarate as the sole electron acceptor was possible. These results demonstrate that, unlike previously described organisms, G. sulfurreducens and possibly G. metallireducens use the same enzyme for both fumarate reduction and succinate oxidation in vivo.