The integral and peripheral proteins of the zymogen granule membrane

Abstract

This study reports the lipid and protein composition of purified pig zymogen granule membranes. Lipids made up more than 70% of the membrane dry weight and phosphatidylserine constituted 17% of the total phospholipids. The membrane was shown to contain nine major proteins. A protein of Mr 92 000 was the major constituent accounting for more than 25% of the Coomassie blue staining on gels. Six glycoproteins, including the latter, were revealed by periodic acid-Schiff staining and concanavalin A binding. A phase separation technique using partition of intrinsic and extrinsic membrane proteins in Triton X-114 solutions has shown that most of the proteins were integral membrane proteins. The ATP diphosphohydrolase, which is distinctive of the zymogen granule membrane, segregated with integral proteins. These data constitute a detailed description of a purified membrane fraction from pig pancreatic zymogen granules.