The initial enzyme for glycosylphosphatidylinositol biosynthesis requires PIG-Y, a seventh component.
Biosynthesis of glycosylphosphatidylinositol (GPI) is initiated by an unusually complex GPI-N-acetylglucosaminyltransferase (GPI-GnT) consisting of at least six proteins. Here, we report that human GPI-GnT requires another component, termed PIG-Y, a 71 amino acid protein with two transmembrane domains. The Burkitt lymphoma cell line Daudi, severely defective in the surface expression of GPI-anchored proteins, was a null mutant of PIG-Y. A complex of six components was formed without PIG-Y. PIG-Y appeared to be directly associated with PIG-A, implying that PIG-Y is the key molecule that regulates GPI-GnT activity by binding directly to the catalytic subunit PIG-A. PIG-Y is probably homologous to yeast Eri1p, a component of GPI-GnT. We did not obtain evidence for a functional linkage between GPI-GnT and ras GTPases in mammalian cells as has been reported for yeast cells. A single transcript encoded PIG-Y and, to its 5' side, another protein PreY that has homologues in a wide range of organisms and is characterized by a conserved domain termed DUF343. These two proteins are translated from one mRNA by leaky scanning of the PreY initiation site.
Murakami
Yoshiko
Y
Department of Immunoregulation, Research Institute for Microbial Diseases, Osaka University, Osaka 565-0871, Japan.
Siripanyaphinyo
Uamporn
U
Hong
Yeongjin
Y
Tashima
Yuko
Y
Maeda
Yusuke
Y
Kinoshita
Taroh
T
D000595:Amino Acid Sequence; D000818:Animals; D016466:CHO Cells; D003001:Cloning, Molecular; D006224:Cricetinae; D003412:Cricetulus; D017261:Glycosylphosphatidylinositols / Q000096:biosynthesis*; D006367:HeLa Cells; D006801:Humans; D016393:Lymphoma, B-Cell; D008565:Membrane Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D017351:N-Acetylglucosaminyltransferases; D017385:Sequence Homology; D014407:Tumor Cells, Cultured; D018631:ras Proteins / Q000378:metabolism
D017261:Glycosylphosphatidylinositols; D008565:Membrane Proteins; C507829:PIGY protein, human; C080086:phosphatidylinositol glycan-class A protein; D017351:N-Acetylglucosaminyltransferases; C037649:N-acetyllactosaminide beta-1,6-N-acetylglucosaminyltransferase; D018631:ras Proteins