4'-AMINO-BENZAMIDO-TAUROCHOLIC ACID SELECTIVELY SOLUBILIZES GLYCOSYL-PHOSPHATIDYLINOSITOL-ANCHORED MEMBRANE-PROTEINS AND IMPROVES LIPOLYTICCLEAVAGE OF THEIR MEMBRANE ANCHORS BY SPECIFIC PHOSPHOLIPASES

Glycosyl-phosphatidylinositol-anchored membrane proteins (GPI-proteins ) are normally identified either by cleavage of the lipid anchor using (glycosyl)phosphatidylinositol-specific phospholipases C or D (GPI-PL s) or by metabolic labeling of the lipid moiety with specific building blocks. Therefore, methods for discrimination between transmembrane p roteins and GPI-proteins on the basis of their physicochemical propert ies are desirable. Here we are presenting a selective extraction metho d for typical well-characterized mammalian GPI-proteins, e.g., acetylc holine esterase, alkaline phosphatase, 5'-nucleotidase, and lipoprotei n lipase, using a derivative of taurocholate. The results were compare d to those obtained with well-characterized transmembrane proteins, e. g., insulin receptor and hydroxymethyl glutaryl coenzyme A-reductase, glucose transporters, or aminopeptidase M and several commercially ava ilable detergents. With regard to total membrane proteins, it was poss ible to selectively enrich GPI-proteins up to 8- to 14-fold by using c oncentrations between 0.1 and 0.3% of 4'-NH2-amino- 7 beta-benzamido-t aurocholic acid (BATC). In addition, the cleavage specificity and effi ciency of (G)PI-PLs were increased in the presence of identical concen trations of BATC compared to commonly used detergents, e.g., Nonidet P -40. Therefore, the present study shows that the use of BATC facilitat es the identification of glycosyl-phosphatidylinositol-anchhored membr ane proteins. (C) 1994 Academic Press, Inc.