Glycolipid membrane-binding domain of human erythrocyte acetylcholinesterase

The membrane-binding domain of human erythrocyte acetylcholinesterase is a small hydrophobic structure at the COOH-terminus of the enzyme subunits. Papain digestion cleaves a COOH-terminal dipeptide linked to the hydrophobic structure with the sequence His-Gly-ethanolamine-Z, where the ethanolamine is in amide linkage to the glycine and Z is a partially characterized glycolipid. This glycolipid includes a second residue of ethanolamine and a residue of glucosamine, both of which have free primary amino groups accesible to radiomethylation. The glycolipid also contains a carbohydrate residue or residues that bind to concanavalin A and nearly stoichiometric amounts of both palmitate and C₂₂ unsaturated fatty acids. Similarities in this membrane-binding structure to those reported for trypanosome variant surface glycoproteins and Thy-1 glycoprotein suggest an important new category of postranslational modifications involving the attachement of COOH-terminal glycolipid.