Occurrence of ether-containing inositol phospholipids in bovine erythrocytes.
Several proteins including bovine erythrocyte acetylcholinesterase are anchored in the membrane through glycoinositol phospholipids containing an alkyl linkage at the sn-1 position of the glycerol. However, the existence of 1-alkyl-2-acyl-sn-glycero-3-phosphoinositol (alkylacyl-GPI) in biological systems has not been demonstrated. In this study, we identified the presence of alkylacyl-GPI in bovine erythrocytes by the following criteria: (1) TLC-Rf value, (2) radyllyso-GPI was produced after phospholipase A2 treatment of the diradyl-GPI, and (3) benzoate derivatives of alkylacylglycerols produced by phospholipase C hydrolysis of diradyl-GPI had the same retention time as that of authentic alkylacylglycerobenzoates on normal-phase HPLC. Diradyl-GPI consisted of 5-10% alkylacyl-GPI. Reverse-phase HPLC analysis of alkylacylglycerobenzoates derived from bovine erythrocyte alkylacyl-GPI showed a multiplicity of species with 18:0-20:4 (11.7%), 16:0-18:1 + 18:0-18:2 (34.9%), and 18:0-18:1 (19.4%) being the major components. Composition of alkyl chains of alkylacyl-GPI from bovine erythrocytes was similar to the reported value for alkylacylglycerols isolated from the glycoinositol phospholipid anchor of bovine erythrocyte acetylcholinesterase. Based on these results, we suggest that alkylacyl-GPI serves as a precursor for the glycoinositol phospholipid of the anchored proteins.
Lee
T C
TC
Medical Sciences Division, Oak Ridge Associated Universities, Tennessee 37831.
Malone
B
B
Buell
A B
AB
Blank
M L
ML
D000110:Acetylcholinesterase / Q000097:blood / Q000737:chemistry; D000818:Animals; D002417:Cattle; D004912:Erythrocytes / Q000737:chemistry*; D006017:Glycolipids / Q000737:chemistry*; D017261:Glycosylphosphatidylinositols; D010716:Phosphatidylinositols / Q000737:chemistry*; D010742:Phospholipid Ethers / Q000737:chemistry*
D006017:Glycolipids; D017261:Glycosylphosphatidylinositols; D010716:Phosphatidylinositols; D010742:Phospholipid Ethers; D000110:Acetylcholinesterase