Lipid, carbohydrate, amino acid, and polypeptide composition of 2 fractions of cell membranes obtained by sucrose-Ficoll zonal density gradient fractionation of gastric mucosal homogenates has been studied. The membranes with density = 1.04 contain 0.7 μmole lipid P and 0.54 μmole cholesterol/mg protein, while the membranes of density 1.10 contain only 0.25 μmole lipid P and 0.28 μmole cholesterol/mg protein. Phosphatidylcholine and phosphatidylethanolamine are the most abundant phospholipids. Free fatty acids were present. Carbohydrates were most abundant in the proteins of the Peak II membranes (density = 1.10). One polypeptide band was dominant on sodium dodecyl sulfate, Triton X-100, and Brij 36T gels, and the adenosine triphosphatase activity in Brij 36T gels was found to have a relative mobility of 0.14 and 0.19 in the two fractions. © 1974.
