Kim Youn Uck, Ashida Hisashi, Mori Kenichiro, Maeda Yusuke, Hong Yeongjin, Kinoshita Taroh
Department of Biological Sciences, Sun Moon University, A-San City, Korea.
J Biochem. 2007 Jul;142(1):123-9. doi: 10.1093/jb/mvm113. Epub 2007 May 22.
GPI mannosyltransferase I (GPI-MT-I) transfers the first mannose to a GPI-anchor precursor, glucosamine-(acyl)phosphatidylinositol [GlcN-(acyl)PI]. Mammalian GPI-MT-I consists of two components, PIG-M and PIG-X, which are homologous to Gpi14p and Pbn1p in Saccharomyces cerevisiae, respectively. In the present study, we disrupted yeast GPI14 and analysed the phenotype of gpi14 yeast. The gpi14 haploid cells were inviable and accumulated GlcN-(acyl)PI. We cloned PIG-M homologues from human, Plasmodium falciparum (PfPIG-M) and Trypanosoma brucei (TbGPI14), and tested whether they could complement gpi14-disrupted yeast. None of them restored GPI-MT-I activity and cell growth in gpi14-disrupted yeast. However, gpi14-disrupted yeast cells with human PIG-M, but not with PfPIG-M or TbGPI14, grew slowly but significantly when they were supplemented with rat PIG-X. This suggests that the association of PIG-X and PIG-M for GPI-MT-I activity is not interchangeable between mammals and the other lower eukaryotes.
糖基磷脂酰肌醇甘露糖基转移酶I（GPI-MT-I）将第一个甘露糖转移至糖基磷脂酰肌醇锚定前体——葡糖胺-（酰基）磷脂酰肌醇[GlcN-（酰基）PI]上。哺乳动物的GPI-MT-I由两个组分组成，即PIG-M和PIG-X，它们分别与酿酒酵母中的Gpi14p和Pbn1p同源。在本研究中，我们破坏了酵母GPI14并分析了gpi14酵母的表型。gpi14单倍体细胞无法存活，并积累了GlcN-（酰基）PI。我们从人、恶性疟原虫（PfPIG-M）和布氏锥虫（TbGPI14）中克隆了PIG-M同源物，并测试它们是否能互补gpi14破坏的酵母。它们均未恢复gpi14破坏酵母中的GPI-MT-I活性和细胞生长。然而，用大鼠PIG-X补充时，携带人PIG-M而非PfPIG-M或TbGPI14的gpi14破坏酵母细胞生长缓慢但显著。这表明PIG-X和PIG-M对于GPI-MT-I活性的关联在哺乳动物和其他低等真核生物之间是不可互换的。
