Detailed studies of [3mcytochalasin B-binding and the inhibition of glucose transport by cytochalasin B have recently permitted characterization of a specific class of D-glucose-inhibitable cytochalasin B-binding sites in purified isolated rat adipose cell plasma membranes, identification of these sites as functional glucose transport systems, and direct demonstration that insulin stimulates gl...

The distribution of free thiol groups associated with the membrane proteins of the purified pig gastric microsomal vesicles was quantified, and the relation of thiol groups to the function of the gastric (H+ + K+)-transporting ATPase system was investigated. Two different thiol-specific agents, carboxypyridine disulphide (CPDS) and N(1-naphthyl)maleimide (NNM) were used for the study. The struc...

Sialoproteins isolated from the soluble fraction of rat liver could be incorporated into microsomal membranes. This incorporation was dependent on protein concentration, time, and temperature. Sodium dodecyl sulfate gel electrophoresis of membrane proteins after in vitro incorporation showed four major sugar-containing peaks and was similar to that found after in vivo labeling. Most of the inco...

A potentiation of CCl4-induced hepatotoxicity was observed in rats pretreated with ethanol 18 hr prior to CCl4 exposure. Hepatic microsomal aldehyde dehydrogenase (ALDH) was significantly inhibited in animals sacrificed 1 hr following the sequential exposure, however, no more so than in those animals receiving CCl4 alone. The animals receiving ethanol alone had ALDH activity similar to vehicle ...

The role of nucleotides in providing energy for polypeptide transfer across the endoplasmic reticulum (ER) membrane is still unknown. To address this question, we treated ER-derived mammalian microsomal vesicles with a photoactivatable analogue of ATP, 8-N3ATP. This treatment resulted in a progressive inhibition of translocation activity. Approximately 20 microsomal membrane proteins were label...

Homogenates of baby-hamster kidney cells and rat embryo fibroblasts prepared by nitrogen cavitation contain a small population of slowly sedimenting mitochondria or mitochondrial fragments, which contaminate the microsomal fraction. This appears to limit the resolution of surface membrane and endoplasmic reticulum on magnesium-containing dextran gradients. The microsomal material and mitochondr...

Phospholipase C was used as a probe for the distribution of phospholipids about the membrane of rough and smooth microsomal fractions from normal and phenobarbital-treated rat liver. All membranes exhibited an asymmetric distribution, with phosphatidylethanolamine and phosphatidylserine concentrated in the inner leaflet of the bilayer and phosphatidylcholine and sphingomyelin concentrated in th...

Cell fractionation experiments indicate that NAD glycohydrolase (EC 3.2.2.6) is a constituent enzyme of both the microsomal (endoplasmic reticulum) and plasmalemma membrane of the rat hepatocyte. The enzyme was solubilized by steapsin digestion from both fractions and subsequently purified -2000 over the homogenate and -500 over the microsomal fraction by successive DEAE-cellulose, Sephadex G-1...