title: PIG-V involved in transferring the second mannose in glycosylphosphatidylinositol.
abstract: Glycosylphosphatidylinositol (GPI) is a glycolipid that anchors many proteins to the eukaryotic cell surface. The biosynthetic pathway of GPI is mediated by sequential additions of sugars and other components to phosphatidylinositol. Four mannoses in the GPI are transferred from dolichol-phosphate-mannose (Dol-P-Man) and are linked through different glycosidic linkages. Therefore, four Dol-P-Man-dependent mannosyltransferases, GPI-MT-I, -MT-II, -MT-III, and -MT-IV for the first, second, third, and fourth mannoses, respectively, are required for generation of GPI. GPI-MT-I (PIG-M), GPI-MT-III (PIG-B), and GPI-MT-IV (SMP3) were previously reported, but GPI-MT-II remains to be identified. Here we report the cloning of PIG-V involved in transferring the second mannose in the GPI anchor. Human PIG-V encodes a 493-amino acid, endoplasmic reticulum (ER) resident protein with eight putative transmembrane regions. Saccharomyces cerevisiae protein encoded in open reading frame YBR004c, which we termed GPI18, has 25% amino acid identity to human PIG-V. Viability of the yeast gpi18 deletion mutant was restored by human PIG-V cDNA. PIG-V has two functionally important conserved regions facing the ER lumen. Taken together, we suggest that PIG-V is the second mannosyltransferase in GPI anchor biosynthesis.
authors.affiliation: Department of Immunoregulation, Research Institute for Microbial Diseases, 3-1 Yamada-oka, Suita, Osaka 565-0871, Japan.
authors.forename: Ji Young
authors.initials: JY
authors.lastname: Kang
authors.forename: Yeongjin
authors.initials: Y
authors.lastname: Hong
authors.forename: Hisashi
authors.initials: H
authors.lastname: Ashida
authors.forename: Nobue
authors.initials: N
authors.lastname: Shishioh
authors.forename: Yoshiko
authors.initials: Y
authors.lastname: Murakami
authors.forename: Yasu S
authors.initials: YS
authors.lastname: Morita
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Maeda
authors.forename: Taroh
authors.initials: T
authors.lastname: Kinoshita
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D016466:CHO Cells; D045744:Cell Line, Tumor; D003001:Cloning, Molecular; D017124:Conserved Sequence; D006224:Cricetinae; D017931:DNA Primers; D005910:Glioma; D017261:Glycosylphosphatidylinositols / Q000378:metabolism*; D006801:Humans; D008358:Mannose / Q000378:metabolism*; D008364:Mannosyltransferases / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D051381:Rats; D015183:Restriction Mapping; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
chemical_list: D017931:DNA Primers; D017261:Glycosylphosphatidylinositols; D008364:Mannosyltransferases; C499655:PIGV protein, rat; D008358:Mannose