title: Fractionation of liver plasma membranes prepared by zonal centrifugation.
abstract: 1. Plasma membranes were isolated from crude nuclear sediments from mouse and rat liver by a rate-dependent centrifugation through a sucrose density gradient contained in the ;A' type zonal rotor. 2. The membranes were further purified by isopycnic centrifugation, and characterized enzymically, chemically and morphologically. 3. When the plasma-membrane fraction of sucrose density 1.17g/cm(3) was dispersed in a tight-fitting homogenizer, two subfractions of densities 1.12 and 1.18 were obtained by isopycnic centrifugation. 4. The light subfraction contained 5'-nucleotidase, nucleoside diphosphatase, leucine naphthylamidase and Mg(2+)-stimulated adenosine triphosphatase activities at higher specific activities than unfractionated membranes. The heavy subfraction was deficient in the above enzymes but contained higher Na(+)+K(+)-stimulated adenosine triphosphatase activity. 5. The light subfraction contained twice as much phospholipid and cholesterol, and three times as much N-acetylneuraminic acid relative to unit protein weight as the heavy subfraction. Polyacrylamide-gel electrophoresis indicated differences in protein composition. 6. Electron microscopy showed the light subfraction to be vesicular. The heavy subfraction contained membrane strips with junctional complexes in addition to vesicles.
mesh_terms: D000251:Adenosine Triphosphatases / Q000032:analysis; D000818:Animals; D002462:Cell Membrane / Q000201:enzymology; D002499:Centrifugation, Density Gradient; D002501:Centrifugation, Zonal; D002784:Cholesterol / Q000032:analysis; D005952:Glucose-6-Phosphatase / Q000032:analysis; D008099:Liver / Q000166:cytology*; D051379:Mice; D008854:Microscopy, Electron; D009438:Neuraminic Acids / Q000032:analysis; D009708:Nucleotidases / Q000032:analysis; D010743:Phospholipids / Q000032:analysis; D010744:Phosphoric Monoester Hydrolases / Q000032:analysis; D051381:Rats; D013385:Succinate Dehydrogenase / Q000032:analysis
chemical_list: D009438:Neuraminic Acids; D010743:Phospholipids; D002784:Cholesterol; D013385:Succinate Dehydrogenase; D009708:Nucleotidases; D010744:Phosphoric Monoester Hydrolases; D005952:Glucose-6-Phosphatase; D000251:Adenosine Triphosphatases