Hrdy Ivan, Hirt Robert P, Dolezal Pavel, Bardonová Lucie, Foster Peter G, Tachezy Jan, Embley T Martin
Department of Parasitology, Charles University, Vinicna 7, 128 44 Prague 2, Czech Republic.
Nature. 2004 Dec 2;432(7017):618-22. doi: 10.1038/nature03149.
Hydrogenosomes are double-membraned ATP-producing and hydrogen-producing organelles of diverse anaerobic eukaryotes. In some versions of endosymbiotic theory they are suggested to be homologues of mitochondria, but alternative views suggest they arose from an anaerobic bacterium that was distinct from the mitochondrial endosymbiont. Here we show that the 51-kDa and 24-kDa subunits of the NADH dehydrogenase module in complex I, the first step in the mitochondrial respiratory chain, are active in hydrogenosomes of Trichomonas vaginalis. Like mitochondrial NADH dehydrogenase, the purified Trichomonas enzyme can reduce a variety of electron carriers including ubiquinone, but unlike the mitochondrial enzyme it can also reduce ferredoxin, the electron carrier used for hydrogen production. The presence of NADH dehydrogenase solves the long-standing conundrum of how hydrogenosomes regenerate NAD+ after malate oxidation. Phylogenetic analyses show that the Trichomonas 51-kDa homologue shares common ancestry with the mitochondrial enzyme. Recruitment of complex I subunits into a H2-producing pathway provides evidence that mitochondria and hydrogenosomes are aerobic and anaerobic homologues of the same endosymbiotically derived organelle.
氢化酶体是多种厌氧真核生物中产生ATP和氢气的双膜细胞器。在一些内共生理论版本中，它们被认为是线粒体的同源物，但也有其他观点认为它们起源于一种与线粒体共生体不同的厌氧细菌。在这里，我们表明，线粒体呼吸链第一步中复合物I的NADH脱氢酶模块的51-kDa和24-kDa亚基在阴道毛滴虫的氢化酶体中具有活性。与线粒体NADH脱氢酶一样，纯化的阴道毛滴虫酶可以还原多种电子载体，包括泛醌，但与线粒体酶不同的是，它还可以还原用于产氢的电子载体铁氧化还原蛋白。NADH脱氢酶的存在解决了长期以来关于氢化酶体在苹果酸氧化后如何再生NAD+的难题。系统发育分析表明，阴道毛滴虫51-kDa同源物与线粒体酶有共同的祖先。复合物I亚基被招募到产氢途径中，这证明线粒体和氢化酶体是同一内共生衍生细胞器的需氧和厌氧同源物。
