Photoaffinity labelling with P3-(4-zidoanilido)uridine 5'-triphosphate identifies Gpi3p as the UDP-GlcNAc-binding subunit of the enzyme that catalyses formation of GlcNAc-phosphatidylinositol, the first glycolipid intermidiate in glycosylphosphatidylinositol synthesis

Z. Kostova, D. M. Rancour, A. K. Menon, P. Orlean

Research output: Contribution to journalArticlepeer-review

Abstract

Glycosylphosphatidylinositols (GPIs) are made by all eukaryores. The first step in their synthesis is the transfer of GlcNAc from UDP-GlcNAc to phosphatidylinositol (PI). Four proteins in mammals and at least three in yeast make up a complex that carries out this reaction. Three of the proteins are highly conserved between yeast and mammals: the Gpi1 protein, the Pig-C/Gpi2 protein and the Pig-A/Gpi3 protein. The function of the individual subunits is not known, but of the three, the Pig-A/Gpi3 proteins resemble members of a large family of nucleotide-sugar-utilizing glycosyltransferases. To establish whether Gpi3p is the UDP-GlcNAc-binding subunit of the yeast GlcNAc-PI synthetic complex, we tested its ability to become cross-linked to the photoactivatable substrate analogue P3-(4-azidoanilido)-uridine 5'-triphosphate (AAUTP). We report that Gpi3p bearing the FLAG epitope at its C-terminus becomes cross-linked to AAUTP[α-32P], but that Gpi2p-FLAG does not. Furthermore, Gpi3p-FLAG expressed in Escherichia coli is also cross-linked. These results indicate that Gpi3p is the UDP-GlcNAc-binding and probable catalytic subunit of the GlcNAc-PI synthetic complex.

Original languageEnglish (US)
Pages (from-to)815-822
Number of pages8
JournalBiochemical Journal
Volume350
Issue number3
DOIs
StatePublished - Sep 15 2000

Keywords

  • Endoplasmic reticulum
  • GPI anchor
  • Glycosyltransferase

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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