title: The glycosylphosphatidylinositol (GPI) signal sequence of human placental alkaline phosphatase is not recognized by human Gpi8p in the context of the yeast GPI anchoring machinery.
abstract: Biosynthesis of glycosylphosphatidylinositol (GPI)-anchored proteins involves the action of a GPI trans-amidase, which replaces the C-terminal GPI signal sequence (GPI-SS) of the primary translation product with a preformed GPI lipid. The transamidation depends on a complex of four proteins, Gaa1p, Gpi8p, Gpi16p and Gpi17p. Although the GPI anchoring pathway is conserved throughout the eukaryotic kingdom, it has been reported recently that the GPI-SS of human placental alkaline phosphatase (hPLAP) is not recognized by the yeast transamidase, but is recognized in yeast that contain the human Gpi8p homologue. This finding suggests that Gpi8p is intimately involved in the recognition of GPI precursor proteins and may also be responsible for the subtle taxon-specific differences in transamidase specificity that sometimes prevent the efficient GPI anchoring of heterologously expressed GPI proteins. Here, we confirm that the GPI signal sequence of hPLAP is indeed not recognized by the yeast GPI-anchoring machinery. However, in our hands, GPI attachment cannot be restored by the co-expression of human Gpi8p in yeast cells under any circumstances.
authors.affiliation: Institute of Biochemistry, University of Fribourg, Switzerland.
authors.forename: Urs
authors.initials: U
authors.lastname: Meyer
authors.forename: Patrick
authors.initials: P
authors.lastname: Fraering
authors.forename: Régine
authors.initials: R
authors.lastname: Bosson
authors.forename: Isabella
authors.initials: I
authors.lastname: Imhof
authors.forename: Mohammed
authors.initials: M
authors.lastname: Benghezal
authors.forename: Christine
authors.initials: C
authors.lastname: Vionnet
authors.forename: Andreas
authors.initials: A
authors.lastname: Conzelmann
mesh_terms: D000469:Alkaline Phosphatase / Q000737:chemistry* / Q000378:metabolism; D019881:Aminoacyltransferases / Q000235:genetics / Q000378:metabolism; D015815:Cell Adhesion Molecules / Q000235:genetics / Q000378:metabolism*; D005260:Female; D017261:Glycosylphosphatidylinositols / Q000378:metabolism*; D006801:Humans; D010920:Placenta / Q000201:enzymology*; D011247:Pregnancy; D021382:Protein Sorting Signals; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D015003:Yeasts / Q000201:enzymology / Q000235:genetics
chemical_list: D015815:Cell Adhesion Molecules; D017261:Glycosylphosphatidylinositols; C491190:PIGK protein, human; D021382:Protein Sorting Signals; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D019881:Aminoacyltransferases; C103133:GPI8 protein, S cerevisiae; C023175:transamidases; D000469:Alkaline Phosphatase