Evidence for a glycolipid anchor of gp64, a putative cell‐cell adhesion protein of Polysphondylium pallidum

Abstract

The membrane‐bound glycoprotein (gp64) of the cellular slime mold Polysphondylium pallidum, is a putative cell‐cell adhesion protein identified by adhesion‐blocking antibody fragments. Since gp64 can be purified in a few days and in substantial yields, it is a good candidate for clarifying the structure of a cell‐cell adhesion protein. This study reveals that gp64 possesses a glycolipid anchor which is sensitive to deamination but resistant to phosphatidylinositol‐specific phospholipase C from Bacillus thuringiensis. Although the anchor resistance to phosphatidylinositol‐specific phospholipase C can be ascribed to the presence of an additional acyl chain on the inositol ring in the glycosyl phosphatidylinositol anchors, this was not the case. After a mild‐base treatment that released an additional acyl chain on the inositol ring, only a trace amount of fatty acid was detected but, after strong acid hydrolysis, we detected both amide‐linked fatty acids and a long‐chain base. The long‐chain base was further analysed by gas‐chromatography/mass spectrometry and was found to be phytosphingosine. Both fatty acids and myo‐inositol were also analysed by gas‐chromatography/mass spectrometry. These data suggest that gp64 possesses a glycolipid anchor which contains ceramide and myo‐inositol. Copyright © 1993, Wiley Blackwell. All rights reserved