Estrone reaches the active site of microsomal UDPglucuronyltransferase (EC 2.4.1.17) via diffusion through the lipid phase of the microsomal membrane (Zakim, D., and Vessey, D. (1977) J. Biol. Chem 252, 7534-7537). The critical aspect of its transport through the cell hence may be delivery of estrone to the microsomal membrane, not to the active site of UDP-glucuronyltransferase. It was thought...

The transverse distribution of enzyme proteins and phospholipids within microsomal membranes was studied by analyzing membrane composition after treatment with proteases and phospholipases. Upon trypsin treatment of closed microsomal vesicles, NADH- and NADPH-cytochrome c reductases as well as cytochrome b5 were solubilized or inactivated, while cytochrome P-450 was partially inactivated. When ...

Microsomes, derived from the endoplasmic reticulum and Golgi fractions, were isolated from rat liver and separated into content and membrane subfractions by treatment with sodium carbonate or by passage through the French pressure cell. The microsomal content contained particles, which had a triglyceride molar concentration tenfold greater than that of phospholipid, cholesterol, and cholesteryl...

Rat liver microsomes and microsomal subfractions isolated by density equilibration were submitted to a quantitative morphological and biochemical analysis. The total area of the endoplasmic reticulum was estimated at 7.3 m(2) per g of liver. The microsome fraction contained 2.8 mg of phospholipids and 6.7 mg of proteins per m(2) of membrane area. After correction for ribosomal and intracisterna...

Despite their importance in many biological processes, membrane proteins are underrepresented in proteomic analysis because of their poor solubility (hydrophobicity) and often low abundance. We describe a novel approach for the identification of plasma membrane proteins and intracellular microsomal proteins that combines membrane fractionation, a centrifugal proteomic reactor for streamlined pr...

The purpose of this study was to simultaneously isolate skeletal muscle plasma and microsomal membranes from the hind limbs of male Sprague-Dawley rats perfused either in the absence or presence of 20 milliunits/ml insulin and to determine the effect of insulin on the number and distribution of glucose transporters in these membrane fractions. Insulin increased hind limb glucose uptake greater ...