Marked Amplification and Diversification of Products of ras Genes from Rat Brain, Rab GTPases, in the Ciliates Tetrahymena thermophila and Paramecium tetraurelia
Marked Amplification and Diversification of Products of ras Genes from Rat Brain, Rab GTPases, in the Ciliates Tetrahymena thermophila and Paramecium tetraurelia
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DOI：
10.1111/j.1550-7408.2010.00503.x
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发表时间：
2010-09
影响因子：
2.2
通讯作者：
Y. Saito-Nakano;Tohru Nakahara;K. Nakano;T. Nozaki;O. Numata
中科院分区：
文献类型：
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作者：
Y. Saito-Nakano;Tohru Nakahara;K. Nakano;T. Nozaki;O. Numata
抽象的。小分子GTP酶Rab(大鼠脑ras基因产物)是真核生物间广泛保守的分子开关，调控膜转运途径。通常认为基因组中编码的Rab基因的数量与多细胞有关，然而，我们发现单细胞纤毛虫四膜虫(Tetrahymena thermophila，TT)和草履虫(Parecium Toururelia，PT)的基因组中含有比HsRab基因多得多的Rab基因。我们成功地从四膜虫基因组中分离到88个TtRab基因的86个克隆。通过比较人和发芽酵母中Rab的氨基酸序列，42个TtRab属于功能亚家族，命名为常规Rab，其余44个TtRab被认为是物种特异性的。为了研究纤毛虫中Rab基因的多样性，我们在四联藻基因组数据库中搜索了Rab基因。总体而言，共发现229个PtRab基因，分别属于157个常规PtRab基因和72个物种特异性PtRab基因。其中，9个PtRab基因与7个TtRab基因高度同源，提示纤毛虫特异性Rab基因的保守性。这些数据表明，纤毛虫中Rab的范围明显扩大和多样化，这可能支持这些生物复杂的细胞结构和旺盛的吞噬作用。
ABSTRACT. Small GTPase Rab (products of ras genes from rat brain) is a widely conserved molecular switch among eukaryotes and regulates membrane trafficking pathways. It is generally considered that the number of Rab encoded in the genome correlates with multicellularity; however, we found that unicellular ciliates Tetrahymena thermophila (Tt) and Paramecium tetraurelia (Pt) possess many more Rab genes in their genome than the 64 HsRab genes in the human genome. We succeeded in isolating 86 cDNA clones of 88 TtRab genes in the Tetrahymena genome. By comparing the amino acid sequence of Rab in humans and the budding yeast Saccharomyces cerevisiae, 42 TtRab belonged to subfamilies functionally characterized and designated as conventional Rab, while the remaining 44 TtRab were considered to be species‐specific. To examine the diversity of Rab in ciliates, we searched for Rab genes in the genome database of P. tetraurelia. Overall, 229 PtRab genes were found and categorized as 157 conventional and 72 species‐specific PtRab, respectively. Among them, nine PtRab genes showed high homology to seven TtRab, suggesting the conservation of ciliate‐specific Rab. These data suggested that the range of Rab is markedly amplified and diversified in ciliates, which may support the elaborate cellular structures and vigorous phagocytosis of those organisms.