Horner D S, Hirt R P, Embley T M
Department of Zoology, Natural History Museum, London, England.
Mol Biol Evol. 1999 Sep;16(9):1280-91. doi: 10.1093/oxfordjournals.molbev.a026218.
The iron sulfur protein pyruvate: ferredoxin oxidoreductase (PFO) is central to energy metabolism in amitochondriate eukaryotes, including those with hydrogenosomes. Thus, revealing the evolutionary history of PFO is critical to understanding the origin(s) of eukaryote anaerobic energy metabolism. We determined a complete PFO sequence for Spironucleus barkhanus, a large fragment of a PFO sequence from Clostridium pasteurianum, and a fragment of a new PFO from Giardia lamblia. Phylogenetic analyses of eubacterial and eukaryotic PFO genes suggest a complex history for PFO, including possible gene duplications and horizontal transfers among eubacteria. Our analyses favor a common origin for eukaryotic cytosolic and hydrogenosomal PFOs from a single eubacterial source, rather than from separate horizontal transfers as previously suggested. However, with the present sampling of genes and species, we were unable to infer a specific eubacterial sister group for eukaryotic PFO. Thus, we find no direct support for the published hypothesis that the donor of eukaryote PFO was the common alpha-proteobacterial ancestor of mitochondria and hydrogenosomes. We also report that several fungi and protists encode proteins with PFO domains that are likely monophyletic with PFOs from anaerobic protists. In Saccharomyces cerevisiae, PFO domains combine with fragments of other redox proteins to form fusion proteins which participate in methionine biosynthesis. Our results are consistent with the view that PFO, an enzyme previously considered to be specific to energy metabolism in amitochondriate protists, was present in the common ancestor of contemporary eukaryotes and was retained, wholly or in part, during the evolution of oxygen-dependent and mitochondrion-bearing lineages.
铁氧化还原蛋白氧化还原酶（PFO）在无线粒体真核生物的能量代谢中起着核心作用，包括那些具有氢化酶体的生物。因此，揭示PFO的进化历史对于理解真核生物厌氧能量代谢的起源至关重要。我们确定了巴氏螺旋体完整的PFO序列、巴氏梭菌PFO序列的一个大片段以及来自贾第虫的一个新PFO片段。对真细菌和真核生物PFO基因的系统发育分析表明，PFO有着复杂的历史，包括真细菌之间可能的基因复制和水平转移。我们的分析支持真核细胞胞质和氢化酶体PFOs来自单一真细菌来源的共同起源，而不是如先前所认为的来自单独的水平转移。然而，基于目前对基因和物种的采样，我们无法推断出真核生物PFO的特定真细菌姐妹群。因此，我们没有找到直接证据支持已发表的假说，即真核生物PFO的供体是线粒体和氢化酶体的共同α-变形菌祖先。我们还报告说，几种真菌和原生生物编码具有PFO结构域的蛋白质，这些蛋白质可能与厌氧原生生物的PFO是单系的。在酿酒酵母中，PFO结构域与其他氧化还原蛋白的片段结合形成融合蛋白，参与甲硫氨酸的生物合成。我们的结果与以下观点一致：PFO这种先前被认为是无线粒体原生生物能量代谢所特有的酶，存在于当代真核生物的共同祖先中，并在需氧和有线粒体谱系的进化过程中被全部或部分保留。
