title: Distribution of membranes, especially of plasma-membrane fragments, during zonal centrifugations of homogenates from glucose-repressed Saccharomyces Cerevisiae.
abstract: 1. The distributions of several enzymes and other marker components were examined after zonal centrifugations of whole homogenates from glucose-repressed Saccharomyces cerevisiae on sucrose and iso-osmotic Ficoll, and the composition and morphology of the fractions were investigated. 2. After high-speed zonal centrifugation most of the protein, acid and alkaline phosphatases, alkaline pyrophosphatase, adenosine monophosphatase, beta-fructofuranosidase, alpha-mannosidase, NADPH-cytochrome c oxidoreductase and an appreciable amount of phospholipid and sterol were non-sedimentable, i.e. were at densities below 1.09 (g/cm3). Most of the RNA was at p=1.06-1.08 in Ficoll and at p=1.09-1.11 in sucrose. 3. The bulk of the Mg2+-dependent adenosine triphosphatase (Mg-ATPase) was coincident with the main peak of phospholipid and sterol, at median density 1.10, which was also rich in smooth-membrane vesicles. In Ficoll, a minor peak of phospholipid and sterol at p-1.12-1.15 contained a smaller part of the oligomycin-insensitive Mg-ATPase and heavy membrane fragments. In sucrose, several minor peaks of Mg-ATPase were in the mitochondrial density range, and a peak of oligomycin-insensitive Mg-ATPase coincident with a minor peak of phospholipid and sterol at around p-1.25 contained heavy membrane fragments of high carbohydrate content, especially mannose. 4. Further purification of the oligomycin-insensitive Mg-ATPase containing membrane preparations was performed on Urografin gradients. 5. It is argued that the oligomycin-insensitive Mg-ATPase containing membranes are fragments of the plasma membrane, but have different densities because they contain different amounts of glycoprotein particles.
mesh_terms: D000135:Acid Phosphatase / Q000032:analysis; D000251:Adenosine Triphosphatases / Q000032:analysis; D000469:Alkaline Phosphatase / Q000032:analysis; D002462:Cell Membrane / Q000201:enzymology*; D002501:Centrifugation, Zonal; D005947:Glucose / Q000494:pharmacology; D008361:Mannosidases / Q000032:analysis; D009251:NADPH-Ferrihemoprotein Reductase / Q000032:analysis; D009708:Nucleotidases / Q000032:analysis; D010743:Phospholipids / Q000032:analysis; D011755:Pyrophosphatases / Q000032:analysis; D012441:Saccharomyces cerevisiae / Q000032:analysis* / Q000201:enzymology; D013261:Sterols / Q000032:analysis
chemical_list: D010743:Phospholipids; D013261:Sterols; D009251:NADPH-Ferrihemoprotein Reductase; D009708:Nucleotidases; D000469:Alkaline Phosphatase; D000135:Acid Phosphatase; D008361:Mannosidases; D000251:Adenosine Triphosphatases; D011755:Pyrophosphatases; D005947:Glucose