Institute of Molecular Biology, University of Oregon, Eugene, OR 97403, USA.
Mol Biol Cell. 2011 Sep;22(17):3176-91. doi: 10.1091/mbc.E11-03-0244. Epub 2011 Jul 7.
The vacuolar-type, proton-translocating ATPase (V-ATPase) is a multisubunit enzyme responsible for organelle acidification in eukaryotic cells. Many organisms have evolved V-ATPase subunit isoforms that allow for increased specialization of this critical enzyme. Differential targeting of the V-ATPase to specific subcellular organelles occurs in eukaryotes from humans to budding yeast. In Saccharomyces cerevisiae, the two subunit a isoforms are the only difference between the two V-ATPase populations. Incorporation of Vph1p or Stv1p into the V-ATPase dictates the localization of the V-ATPase to the vacuole or late Golgi/endosome, respectively. A duplication event within fungi gave rise to two subunit a genes. We used ancestral gene reconstruction to generate the most recent common ancestor of Vph1p and Stv1p (Anc.a) and tested its function in yeast. Anc.a localized to both the Golgi/endosomal network and vacuolar membrane and acidified these compartments as part of a hybrid V-ATPase complex. Trafficking of Anc.a did not require retrograde transport from the late endosome to the Golgi that has evolved for retrieval of the Stv1p isoform. Rather, Anc.a localized to both structures through slowed anterograde transport en route to the vacuole. Our results suggest an evolutionary model that describes the differential localization of the two yeast V-ATPase isoforms.
液泡型质子泵（V-ATPase）是一种多亚基酶，负责真核细胞细胞器的酸化。许多生物体已经进化出 V-ATPase 亚基同工型，从而使这种关键酶能够实现更高的专业化。从人类到芽殖酵母等真核生物中，V-ATPase 都能够特异性靶向特定的亚细胞细胞器。在酿酒酵母中，两种亚基 a 同工型是两种 V-ATPase 群体之间的唯一区别。Vph1p 或 Stv1p 的掺入决定了 V-ATPase 分别定位于液泡或晚期高尔基体/内体。真菌中的基因复制事件产生了两个亚基 a 基因。我们使用祖先基因重建生成了 Vph1p 和 Stv1p 的最近共同祖先（Anc.a），并在酵母中测试了其功能。Anc.a 定位于高尔基体/内体网络和液泡膜，并作为混合 V-ATPase 复合物的一部分酸化这些隔室。Anc.a 的运输不需要从晚期内体逆行运输到高尔基体，这是为了回收 Stv1p 同工型而进化的。相反，Anc.a 通过在前往液泡的途中减缓正向运输而定位于这两种结构。我们的结果提出了一个进化模型，描述了两种酵母 V-ATPase 同工型的差异定位。
