Lin Winston, Whitman William B
Department of Microbiology, University of Georgia, Athens, GA 30602-2605, USA.
Arch Microbiol. 2004 Jan;181(1):68-73. doi: 10.1007/s00203-003-0629-1. Epub 2003 Dec 4.
The operon of the anabolic pyruvate oxidoreductase (POR) of Methanococcus maripaludis encodes two genes ( porEF) whose functions are unknown. Because these genes possess sequence similarity to polyferredoxins, they may be electron carriers to the POR. To elucidate whether the methanococcal POR requires PorEF for activity, a deletion mutant, strain JJ150, lacking porEF was constructed. Compared to the wild-type strain JJ1, the mutant grew more slowly in minimal medium and minimal plus acetate medium, and pyruvate-dependent methanogenesis was inhibited. In contrast, the methyl-viologen-dependent pyruvate-oxidation activity of POR, carbon monoxide dehydrogenase, and hydrogenase activities of the mutant were similar to those of the wild-type. Upon genetic complementation of the mutant with porEF in the methanococcal shuttle vector pMEV2+ porEF, growth in minimal medium and pyruvate-dependent methanogenesis were restored to wild-type levels. Complementation with porE alone restored methanogenesis from pyruvate but not growth in minimal medium. Complementation with porF alone partially restored growth but not methanogenesis from pyruvate. Although the specific roles of porE and porF have not been determined, these results suggest that PorEF play important roles in the anabolic POR in vivo even though they are not required for the dye-dependent activity.
沼泽红球菌合成代谢型丙酮酸氧化还原酶（POR）的操纵子编码两个基因（porEF），其功能尚不清楚。由于这些基因与多铁氧化还原蛋白具有序列相似性，它们可能是POR的电子载体。为了阐明产甲烷球菌POR的活性是否需要PorEF，构建了一个缺失porEF的缺失突变体菌株JJ150。与野生型菌株JJ1相比，该突变体在基本培养基和添加乙酸盐的基本培养基中生长较慢，并且丙酮酸依赖性产甲烷作用受到抑制。相反，该突变体的POR的甲基紫精依赖性丙酮酸氧化活性、一氧化碳脱氢酶活性和氢化酶活性与野生型相似。用产甲烷球菌穿梭载体pMEV2 + porEF中的porEF对该突变体进行基因互补后，在基本培养基中的生长和丙酮酸依赖性产甲烷作用恢复到野生型水平。单独用porE互补可恢复丙酮酸的产甲烷作用，但不能恢复在基本培养基中的生长。单独用porF互补可部分恢复生长，但不能恢复丙酮酸的产甲烷作用。尽管尚未确定porE和porF的具体作用，但这些结果表明，PorEF在体内合成代谢型POR中起重要作用，尽管它们对于染料依赖性活性不是必需的。
