Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: HUMANGGP:036206 (endoplasmic reticulum)
 63,868 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

On the basis of association with endoplasmic reticulum membranes, poyribosomes isolated from mouse myeloma MOPC-104E were separated into two classes, membrane bound and free. The membrane-bound and free polyribosomes were then compared for their capacity to incorporate [35S]methionine into A-particle proteins in vitro. As revealed by a radioimmunological assay method, labeling of A-particle protein occurred with the membrane-bound polyribosomes but not with the free polyribosomes. Peptide mapping of the immunoprecipitated, in vitro [35S]methionine-labeled product confirmed that A-particle protein had been synthesized in vitro.
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PMID:In vitro synthesis of A-particle structual protein by membrane-bound polyribosomes. 17 15

The association of vesicular stomatitis virus proteins with intracellular and plasma membranes was examined by pulse and pulse-chase labeling of virus-infected HeLa cells with [35S]methionine and separation of cell homogenates into three major membrane fractions in discontinuous sucrose gradients. The glycoprotein G was primarily associated with rough endoplasmic reticulum-like membranes after short radioactive pulses (2 to 4 min) but accumulated in the plasma membrane-enriched fraction and the smooth internal membrane fraction with longer pulse or chase periods. The nucleocapsid protein N and the matrix protein M accumulated in the rough endoplasmic reticulum and plasma membrane-like fractions but not in the smooth internal membrane fraction. Only a fraction (35 to 40%) of the viral protein synthesized during a short pulse in the mid-cycle of infection was apparently utilized in released virus. The newly synthesized virus proteins first appeared in released virus in the order: M, N and L, and G.
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PMID:Association of vesicular stomatitis virus proteins with HeLa cell membranes and released virus. 18 39

Previous work has shown that the mRNA encoding the vesicular stomatitis virus (VSV) glycoprotein (G) is bound to the rough endoplasmic reticulum (RER) and that newly made G protein is localized to the RER. In this paper, we have investigated the topology and processing of the newly synthesized G protein in microsomal vesicles. G was labeled with [35S]methionine ([35S]met), either by pulse-labeling infected cells or by allowing membrane-bound polysomes containing nascent G polipeptides to complete G synthesis in vitro. In either case, digestion of microsomal vesicles with any of several proteases removes approximately 5% (30 amino acids) from each G molecule. These proteases will digest the entire G protein if detergents are present during digestion. Using the method of Dintzis (1961, Proc. Natl. Acad. Sci. U. S. A. 47:247--261) to order tryptic peptides (8), we show that peptides lost from G protein by protease treatment of closed vesicles are derived from the carboxyterminus of the molecule. The newly made VSV G in microsomal membranes is glycosylated. If carbohydrate is removed by glycosidases, the resultant peptide migrates more rapidly on polyacrylamide gels than the unglycosylated, G0, form synthesized in cell-free systems in the absence of membranes. We infer that some proteolytic cleavage of the polypeptide backbone is associated with membrane insertion of G. Further, our findings demonstrate that, soon after synthesis, G is found in a transmembrane, asymmetric orientation in microsomal membranes, with its carboxyterminus exposed to the extracisternal, or cytoplasmic, face of the vesicles, and with most or all of its amino-terminal peptides and its carbohydrate sequestered within the bilayer and lumen of the microsomes.
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PMID:Transmembrane biogenesis of the vesicular stomatitis virus glycoprotein. 22 71

The sequential pattern of lipid accumulation and associated biochemical changes were studied in two commonly used experimental models of nutritional fatty liver in rats. Female rats were maintained for 8 weeks on high fat, low protein diets containing adequate methionine and choline, and drinking water ad libitum (Diet 1), or deficient in methionine and choline and containing 20% ethanol as a substitute for drinking water (Diet 2). Histologically, there was a progressive increase in liver lipids, mainly in the periportal areas. Occasional foci of liver cell necrosis with lipogranuloma formation occurred in areas of severe fatty change. These changes appeared earlier and were more marked in rats maintained on Diet 2. Electron micrographs revealed large lipid droplets in the liver cells, which sometimes contained myelin figures. The mitochondria were enlarged, distorted and appeared as amorphous structures with disorientated cristae in rats on Diet 1, whereas they had a condensed conformation in rats maintained on Diet 2. Rough endoplasmic reticulum was fragmented and degranulated particularly in rats on Diet 1, and smooth endoplasmic reticulum showed hyperplasia and vesiculation in rats on Diet 2. There was a progressive increase in the total liver lipids and triglycerides in both the groups of rats. This fatty change was accompanied by a significant increase in hepatic 3-hydroxybutyrate, acetoacetate, malate, 2-oxoglutarate, citrate, lactate, ammonia, glutamate, alanine and aspartate, and a significant decrease in oxaloacetate, urea and glucose concentrations. The mass action ratios for alanine aminotransferase, aspartate amino transferase, and glutamate dehydrogenase, generally moved in a parallel direction. Hepatic ATP content was considerably reduced accompanied by a decrease in [ATP]/[ADP] ratios and a significant increased in [lactate]/[pyruvate] and [3-hydroxybutyrate]/[acetoacetate] ratios. There was a corresponding decrease in the [NAD+]/[NADH] ratios both in the cytoplasmic and mitochondrial compartments. These biochemical changes were particularly severe in rats maintained on Diet 1 and Diet 2 for 8 weeks. There was a very good relationship between impaired mitochondrial and endoplasmic reticulum functions, redox and phosphorylation states, and the relevance of their changes to the fate of fatty liver cells.
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PMID:Lipid accumulation in the rat liver: a histological and biochemical study. 23

Opsin, the apoprotein of the visual pigment rhodopsin, is synthesized on membranes of the rough endoplasmic reticulum and subsequently passes through the Golgi apparatus to the rod outer segment. This pathway parallels the early stages of biosynthesis of some secretory proteins and viral membrane glycoproteins. Most of these proteins are initially synthesized as precursor molecules with a short-lived hydrophobic extra peptide segment at the NH(2) terminus. Therefore we investigated whether or not the immediate translation product of opsin mRNA contains a similar short-lived NH(2)-terminal extra peptide. The mRNA coding for opsin was isolated from bovine retina polysomes precipitated by antibodies to opsin. The mRNA directed the cell-free synthesis of a protein comparable in size to opsin that was specifically precipitated by anti-opsin antibodies. Sequence analyses of the immunoprecipitated protein labeled with six radioactive amino acids (Met, Asn, Pro, Phe, Tyr, Val) provided the following result: [Formula: see text] (X is unknown). This partial sequence of the cell-free product corresponds exactly to the published NH(2)-terminal segment of native opsin (21 residues long) and extends beyond this region. Met-1 was shown to be the initiator methionine residue, because only the initiator [(35)S]Met-tRNA(1) (Met)-not the internal [(35)S]Met-tRNA(2) (Met)-donated the NH(2)-terminal methionine. This finding essentially rules out the possibility that Met-1 was preceded by a peptide that was rapidly cleaved. Thus opsin, and not a precursor, is the immediate product of opsin mRNA translation.
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PMID:Messenger RNA of opsin from bovine retina: isolation and partial sequence of the in vitro translation product. 28 54

The use of L-[35S]methionine (500-700 Ci/mmol (1 Ci = 37 GBq) for labelling the polypeptides of liver rough (R) and smooth (S)endoplasmic reticulum (ER) membrane fractions in vivo was studied. Adult mice were injected intraperitoneally with 400 muCi of the isotope and killed at various times (2'min to 24 h) thereafter. RER and SER fractions were prepared, stripped of ribosomes, and treated with Triton X-100 to remove intravesicular contents. Sufficient radioactivity was present in individual aliquots (75 microgram protein) of the ER membrane fractions to permit their analysis by fluorography after separation by electrophoresis in polyacrylamide gels containing sodium dodecyl sulphate. By 3 min, although the majority of the labelled components were of intravesicular origin, some 12 membrane polypeptides were labelled in the RER fraction (including one corresponding in migration to cytochrome P-450); some 6 of these latter polypeptides were labelled to a lesser degree in the SER membrane fraction at this time. By 5 min, the patterns of radioactive polypeptides of the RER and SER fractions (including both membrane and intravesicular components) were identical. By 7 min, some 28 labelled membrane polypeptides were detectable in the total microsomal membrane. Analysis of the 24-h samples revealed that all the membrane polypeptides seen by staining with Coomassie blue were visualised by fluorography. Other studies revealed the applicability of the approach used for producing highly labelled cell sap and serum proteins. The overall results demonstrate the suitability of L-[35S]methionine administered in vivo for producing mouse liver ER membrane polypeptides of relatively high radioactivity and are consistent with a rapid conversion of RER to SER by ribosome detachment or membrane flow.
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PMID:Suitability of L-[35S]methionine for studying the biosynthesis of the polypeptides of mouse liver endoplasmic reticulum membrane fractions in vivo. 47 10

An ultrastructural study of cerebral cortex was performed in rats during the preictal period following the administration of the convulsant methionine sulfoximine (MSO). The morphologic changes were restricted to astrocytes and consisted of cytoplasmic enlargement, mitochondrial and rough endoplasmic reticulum proliferation, accumulation of glycogen, development of cisternal and saccular smooth endoplasmic reticulum, nuclear chromatin clumping, and hydropic degenerative changes. These findings resemble those seen in experimental ammonia encephalopathy, suggesting an important role of ammonia in the evolution of these morphologic changes. The findings, moreover, suggest that the primary effect of MSO is on astrocytes and that abnormalities in astrocytes may play a role in the development of MSO-induced seizures.
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PMID:Ultrastructural study of methionine sulfoximine-induced Alzheimer type II astrocytosis. 55 86

The effect of colchicine, Nocodazole, and dibucaine on the assembly of Semliki Forest virus was investigated. Colchicine, Nocodazole, and dibucaine reduced the production of extracellular virus by 75 to 90%. Lumicolchicine had no effect on virus growth. Other control experiments showed no effect by these drugs on the incorporation of [3H]leucine into material precipitated by trichloroacetic acid. Colchicine (100 micron) disrupted the microtubles of the baby hamster kidney cells (BHK-21), whereas dibucaine did not alter microtubule polymerization. The stage of virus assembly inhibited by colchicine and dibucaine was studied by experiments with [3H]-leucine or [35S]methionine. At various times after addition of one of these drugs, the incorporation of the labeled precursors into viral proteins associated with fractions enriched for endoplasmic reticulum or plasma membrane from the cell was evaluated. The results clearly show that the envelope and nucleocapsid proteins of the virus move to the plasma membrane of the cell where they accumulate. The studies strongly suggest that the cytoskeletal system is involved in the final stages of morphogenesis of Semliki Forest virus from the plasma membrane.
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PMID:The effect of colchicine and dibucaine on the morphogenesis of Semliki Forest virus. 65 35

During development from fetal to adult age in the female rat the rapid increase of hepatic drug metabolizing activity was paralleled by changes in the production of membrane bound phospholipids. Microsomal phosphatidylcholine synthesis was raised in particular, and was associated with an enhanced activity of S-adenosyl-L-methionine:microsomal phosphatidylethanolamine methyl transferase. This enzyme is responsible, in part, for phosphatidylcholine production by stepwise methylation. Phospholipid acyl components such as various unsaturated fatt acids also showed a sharp rise during development. These results demonstrated that maturation of the hepatic endoplasmic reticulum was correlated with an increased production of phosphatidylcholine that contained greater amounts of unsaturated fatty acids. It is therefore suggested that during maturation phospholipids are not only essential in providing the structural units of the membranes but they also act as organizers of enzyme function.
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PMID:Role of phospholipids in the development of the hepatic endoplasmic reticulum associated with drug metabolism. 73 33

The ultrastructure of the rat cerebellar cortex and the activity of succinic dehydrogenase were examined during methionine sulphoximine (MSO)-provoked convulsions. The animals were killed 3, 6 and 12 hours after the injection of 600 mg/kg of MSO. Convulsions appeared 4--5 hours, status epilepticus developed 8-9 hours after the injection. Progressive ischaemic changes of Purkinje cells could be observed, with condensation of the nucleus and a density of the cytoplasmic matrix. The cisternae of the Golgi complex and endoplasmic reticulum showed some degree of dilation. The basis of Purkinje cells was surrounded by distorted axons and terminals that had lost in most cases the synaptic vesicles, and by clear spaces due to the swollen glial processes. Three to six hours after MSO injection, succinic dehydrogenase activity increased in the mitochondria of Purkinje cells. After the appearance of seizures the enzyme activity decreased. Twelve hours after the injection the enzyme activity recovered to a certain extent.
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PMID:Ultrastructural changes in the rat cerebellar cortex during methionine sulphoximine convulsions. 74 16


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