Phosphatidylethanolamine is the donor of the phosphorylethanolamine linked to the alpha1,4-linked mannose of yeast GPI structures.
Glycosylphosphatidylinositol (GPI) anchors of all species contain the core structure protein-CO-NH-(CH(2))(2)-PO(4)-Manalpha1-2Manalpha1-6Manalpha1-4GlcNalpha1-6inositol-PO(4)-lipid. In recent studies in yeast it was found that gpi10-1 mutants accumulate M2, an abnormal intermediate having the structure Manalpha1-6[NH(2)-(CH(2))(2)-PO(4)-->]Manalpha1-4GlcNalpha1-6(acyl-->)inositol-PO(4)-lipid. It thus was realized that yeast GPI lipids, as their mammalian counterparts, contain an additional phosphorylethanolamine side chain on the alpha1,4-linked mannose. The biosynthetic origin of this phosphorylethanolamine group was investigated using gpi10-1 Deltaept1 Deltacpt1, a strain which is unable to synthesize phosphatidylethanolamine by transferring phosphorylethanolamine from CDP-ethanolamine onto diacylglycerol, but which still can make phosphatidylethanolamine by decarboxylation of phosphatidylserine. Gpi10-1 Deltaept1 Deltacpt1 triple mutants are unable to incorporate [(3)H]ethanolamine into M2 although metabolic labeling with [(3)H]inositol demonstrates that they make as much M2 as gpi10-1. In contrast, when labeled with [(3)H]serine, the triple mutant incorporates more label into M2 than gpi10-1. This result establishes that the phosphorylethanolamine group on the alpha1,4-linked mannose is derived from phosphatidylethanolamine and not from CDP-ethanolamine.
Imhof
I
I
Institute of Biochemistry, University of Fribourg, CH-1700 Fribourg, Switzerland.
Canivenc-Gansel
E
E
Meyer
U
U
Conzelmann
A
A
D002240:Carbohydrate Sequence; D004983:Ethanolamines / Q000737:chemistry*; D017261:Glycosylphosphatidylinositols / Q000737:chemistry*; D008358:Mannose / Q000737:chemistry*; D008969:Molecular Sequence Data; D010714:Phosphatidylethanolamines / Q000737:chemistry*; D012441:Saccharomyces cerevisiae / Q000737:chemistry*
D004983:Ethanolamines; D017261:Glycosylphosphatidylinositols; D010714:Phosphatidylethanolamines; C005448:phosphorylethanolamine; D008358:Mannose