Tomita S, Inoue N, Maeda Y, Ohishi K, Takeda J, Kinoshita T
Department of Immunoregulation, Research Institute for Microbial Diseases, Osaka University, Osaka, Japan.
J Biol Chem. 1998 Apr 10;273(15):9249-54. doi: 10.1074/jbc.273.15.9249.
Dolichol-phosphate-mannose (Dol-P-Man) serves as a donor of mannosyl residues in major eukaryotic glycoconjugates. It donates four mannosyl residues in the N-linked oligosaccharide precursor and all three mannosyl residues in the core of the glycosylphosphatidylinositol anchor. In yeasts it also donates one mannose to the O-linked oligosaccharide. The yeast DPM1 gene encodes a Dol-P-Man synthase that is a transmembrane protein expressed in the endoplasmic reticulum. We cloned human and mouse homologues of DPM1, termed hDPM1 and mDPM1, respectively, both of which encode proteins of 260 amino acids, having 30% amino acid identity with yeast Dpm1 protein but lacking a hydrophobic transmembrane domain, which exists in the yeast synthase. Human and mouse DPM1 cDNA restored Dol-P-Man synthesis in mouse Thy-1-deficient mutant class E cells. Mouse class E mutant cells had an inactivating mutation in the mDPM1 gene, indicating that mDPM1 is the gene for class E mutant. In contrast, hDPM1 and mDPM1 cDNA did not complement another Dol-P-Man synthesis mutant, hamster Lec15 cells, whereas yeast DPM1 restored both mutants. Therefore, in contrast to yeast, mammalian cells require hDPM1/mDPM1 protein and a product of another gene that is defective in Lec15 mutant cells for synthesis of Dol-P-Man.
多萜醇磷酸甘露糖（Dol-P-Man）作为主要真核生物糖缀合物中甘露糖基残基的供体。它在N-连接寡糖前体中提供四个甘露糖基残基，在糖基磷脂酰肌醇锚定物的核心中提供所有三个甘露糖基残基。在酵母中，它还向O-连接寡糖提供一个甘露糖。酵母DPM1基因编码一种多萜醇磷酸甘露糖合酶，该酶是一种在内质网中表达的跨膜蛋白。我们克隆了DPM1的人类和小鼠同源物，分别称为hDPM1和mDPM1，它们都编码260个氨基酸的蛋白质，与酵母Dpm1蛋白具有30%的氨基酸同一性，但缺乏酵母合酶中存在的疏水跨膜结构域。人类和小鼠DPM1 cDNA恢复了小鼠Thy-1缺陷型E类细胞中的Dol-P-Man合成。小鼠E类突变细胞在mDPM1基因中有一个失活突变，表明mDPM1是E类突变的基因。相比之下，hDPM1和mDPM1 cDNA不能互补另一个Dol-P-Man合成突变体，仓鼠Lec15细胞，而酵母DPM1能恢复这两个突变体。因此，与酵母不同，哺乳动物细胞需要hDPM1/mDPM1蛋白和Lec15突变细胞中缺陷的另一个基因的产物来合成Dol-P-Man。
