Genetics of Microorganisms, Department of Life Sciences, Université de Liège, Belgium.
Mol Biol Evol. 2010 Jul;27(7):1630-44. doi: 10.1093/molbev/msq049. Epub 2010 Feb 15.
In yeast, mammals, and land plants, mitochondrial F(1)F(O)-ATP synthase (complex V) is a remarkable enzymatic machinery that comprises about 15 conserved subunits. Peculiar among eukaryotes, complex V from Chlamydomonadales algae (order of chlorophycean class) has an atypical subunit composition of its peripheral stator and dimerization module, with nine subunits of unknown evolutionary origin (Asa subunits). In vitro, this enzyme exhibits an increased stability of its dimeric form, and in vivo, Chlamydomonas reinhardtii cells are insensitive to oligomycins, which are potent inhibitors of proton translocation through the F(O) moiety. In this work, we showed that the atypical features of the Chlamydomonadales complex V enzyme are shared by the other chlorophycean orders. By biochemical and in silico analyses, we detected several atypical Asa subunits in Scenedesmus obliquus (Sphaeropleales) and Chlorococcum ellipsoideum (Chlorococcales). In contrast, complex V has a canonical subunit composition in other classes of Chlorophytes (Trebouxiophyceae, Prasinophyceae, and Ulvophyceae) as well as in Streptophytes (land plants), and in Rhodophytes (red algae). Growth, respiration, and ATP levels in Chlorophyceae were also barely affected by oligomycin concentrations that affect representatives of the other classes of Chlorophytes. We finally studied the function of the Asa7 atypical subunit by using RNA interference in C. reinhardtii. Although the loss of Asa7 subunit has no impact on cell bioenergetics or mitochondrial structures, it destabilizes in vitro the enzyme dimeric form and renders growth, respiration, and ATP level sensitive to oligomycins. Altogether, our results suggest that the loss of canonical components of the complex V stator happened at the root of chlorophycean lineage and was accompanied by the recruitment of novel polypeptides. Such a massive modification of complex V stator features might have conferred novel properties, including the stabilization of the enzyme dimeric form and the shielding of the proton channel. In these respects, we discuss an evolutionary scenario for F(1)F(O)-ATP synthase in the whole green lineage (i.e., Chlorophyta and Streptophyta).
在酵母、哺乳动物和陆地植物中，线粒体 F(1)F(O)-ATP 合酶（复合物 V）是一种由约 15 个保守亚基组成的卓越酶机制。在真核生物中，来自绿藻门（绿藻纲）的衣滴虫（Chlamydomonadales）藻类的复合物 V 具有其外周定子和二聚化模块的非典型亚基组成，具有九个未知进化起源的亚基（Asa 亚基）。在体外，这种酶表现出其二聚体形式的稳定性增加，并且在体内，莱茵衣藻（Chlamydomonas reinhardtii）细胞对寡霉素不敏感，寡霉素是质子通过 F(O)部分转移的有效抑制剂。在这项工作中，我们表明 Chlamydomonadales 复合物 V 酶的非典型特征与其他绿藻目共享。通过生化和计算机分析，我们在斜生栅藻（Sphaeropleales）和椭圆小球藻（Chlorococcales）中检测到几个非典型的 Asa 亚基。相比之下，其他绿藻纲（Trebouxiophyceae、Prasinophyceae 和 Ulvophyceae）以及石松类（陆地植物）和红藻（红藻）中的复合物 V 具有典型的亚基组成。绿藻纲的生长、呼吸和 ATP 水平也几乎不受影响寡霉素浓度影响其他绿藻类的代表。我们最后通过在莱茵衣藻（C. reinhardtii）中使用 RNA 干扰研究了 Asa7 非典型亚基的功能。尽管 Asa7 亚基的缺失对细胞生物能量或线粒体结构没有影响，但它会使体外酶二聚体形式不稳定，并使生长、呼吸和 ATP 水平对寡霉素敏感。总的来说，我们的结果表明，复合物 V 定子的典型成分的缺失发生在绿藻系的根部，并伴随着新多肽的招募。这种对复合物 V 定子特征的大规模修饰可能赋予了新的特性，包括酶二聚体形式的稳定和质子通道的屏蔽。在这些方面，我们讨论了整个绿色谱系（即绿藻门和石松类）中 F(1)F(O)-ATP 合酶的进化情况。
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