A SAS-6-Like Protein Suggests that the Toxoplasma Conoid Complex Evolved from Flagellar Components
A SAS-6-Like Protein Suggests that the Toxoplasma Conoid Complex Evolved from Flagellar Components
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DOI：
10.1128/ec.00096-13
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发表时间：
2013-07-01
期刊：
影响因子：
--
通讯作者：
Morrissette, Naomi S.
中科院分区：
文献类型：
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作者：
de Leon, Jessica Cruz;Scheumann, Nicole;Morrissette, Naomi S.
SAS-6是不同真核生物中心粒生物发生所必需的。在这里，我们描述了一个新的家庭SAS-6样（SAS 6L）的蛋白质，共享一个N-末端结构域与SAS-6，但缺乏卷曲螺旋尾巴。SAS-6蛋白存在于含有SAS-6的真核生物亚群中，包括多种原生动物和绿色藻类。在顶复形寄生虫弓形虫中，SAS-6定位于中心粒，但SAS 6L被发现在圆锥体上方，圆锥体是一种在蜂窝状生物体子集的顶端发现的含微管蛋白的神秘结构。SAS 6L的缺失导致弓形虫的适应性降低。布氏锥虫同源物SAS 6L定位于基板区域，在轴丝中心对微管有核的网站。当内源性SAS 6L在弓形虫速殖子或锥虫锥鞭毛体中过表达时，它形成延伸穿过细胞质的突出细丝，这表明尽管缺乏卷曲螺旋结构域，但它保留了形成更高级结构的能力。我们的结论是，虽然SAS 6L蛋白与SAS-6共享一个保守结构域，但它们是一个功能不同的家族，早于真核生物的最后一个共同祖先。此外，在锥虫和弓形虫中的SAS 6L蛋白的独特定位增加了重量的假设，即锥状复合体从鞭毛组件演变而来。
SAS-6 is required for centriole biogenesis in diverse eukaryotes. Here, we describe a novel family of SAS-6-like (SAS6L) proteins that share an N-terminal domain with SAS-6 but lack coiled-coil tails. SAS6L proteins are found in a subset of eukaryotes that contain SAS-6, including diverse protozoa and green algae. In the apicomplexan parasite Toxoplasma gondii, SAS-6 localizes to the centriole but SAS6L is found above the conoid, an enigmatic tubulin-containing structure found at the apex of a subset of alveolate organisms. Loss of SAS6L causes reduced fitness in Toxoplasma. The Trypanosoma brucei homolog of SAS6L localizes to the basal-plate region, the site in the axoneme where the central-pair microtubules are nucleated. When endogenous SAS6L is overexpressed in Toxoplasma tachyzoites or Trypanosoma trypomastigotes, it forms prominent filaments that extend through the cell cytoplasm, indicating that it retains a capacity to form higher-order structures despite lacking a coiled-coil domain. We conclude that although SAS6L proteins share a conserved domain with SAS-6, they are a functionally distinct family that predates the last common ancestor of eukaryotes. Moreover, the distinct localization of the SAS6L protein in Trypanosoma and Toxoplasma adds weight to the hypothesis that the conoid complex evolved from flagellar components.