| Research Abstract |
Our goal is to clarify molecular mechanisms of GPI anchor biosynthesis. During last two years we have made following three progresses. 1) Early steps. We cloned human GPI1 and showed that PIG-A, PIG-H, PIG-C and GPI1 proteins farm a complex and that the protein complex is the N-acetylglucosaminyl transferase that mediates the first step (Watanabe et al., EMBO J, 1998, 17 : 877-885). We demonstrated that PIG-L is the N-acetyiglucosaminyl phosphatidylinositol de-N-acetylase that mediates the second step (Watanabe et al, Biochemical J, in press).
2) Regarding biosynthesis of dolichol-phosphate-mannose (Dol-P-Man), a donor of three mannoses used in GPI, we showed that a mammalian homologue of yeast Dol-P-Man synthase Dpmlp is not sufficient for biosynthesis of Dol-P-Man in mammalian cells (Tomita et al, J Biol Chem, 1998, 273 : 9249-9254). We then cloned rat DPM2 and showed that Dpm2p is necessary for stable expression and localization of catalytic Dpmlp in the endoplasmic reticulum (Maeda et al, EMBO J, 1998, 17 : 4920-4929).
3) Regarding an enzyme that transfers preassembled GPI to proteins, we demonstrated that GAA1 is a subunit that recognizes GPI attachment signal sequence (Ohishi et al, submitted for publication).
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