Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0155339 (Brown)
 12,436 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Liver microsomal 3-hydroxy-3-methylglutaryl-CoA reductase was partially purified from cholestyramine-fed rats by sequential extraction of the membrane with 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS) and polyethylene glycol nonylphenyl ether (Triton N-101) and solubilized by incorporation of the resulting insoluble protein preparation into a detergent mixture of Triton N-101 and sodium N-lauroylsarcosinate (Sarkosyl) in the presence of high salt. The purification procedure resulted in approximately a 3-4-fold increase in specific activity compared with the microsomal fraction, and the enzyme was recovered with yields as high as 63%. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and a blotting experiment using antiserum to the purified 53,000-dalton reductase fragment showed that the major immunoreactive polypeptide had a Mr of 97,000, that expected for the native intact form of the enzyme (Chin, D. J., Gil, G., Russell, D. W., Liscum, L., Luskey, K. L., Basu, S. K., Okayama, H., Berg, P., Goldstein, J. L., and Brown, M. S. (1984) Nature 308, 613-617). In addition, the effect of various detergents on the activity and stability of the membrane-bound and the partially purified enzyme was determined, and a method for protection of the reductase from inactivation caused by the addition of anionic detergents to the assay mixture is described.
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PMID:Solubilization of the 97-kDa native form of liver microsomal 3-hydroxy-3-methylglutaryl-coenzyme A reductase. 235 84

Previous investigations [Jones, Brown, von Glos & Gaunt (1985) Exp. Cell Res. 156, 31-44] have demonstrated the appearance of a new antigenic determinant (recognized by monoclonal antibody 2D6) on the plasma membrane of rat spermatozoa during post-testicular maturation in the epididymis. Identification of the 2D6 antigen on Western blots from one-dimensional SDS/polyacrylamide gels revealed that it co-migrated with a membrane protein (designated Mr 23,000 antigen) present on testicular and immature germ cells, suggesting that one antigen might be a modified version of the other. In the present work, however, we demonstrate that, although they have similar Mr and are present in soluble and membrane-bound forms, the 2D6 and Mr 23,000 antigens are biochemically and immunologically distinct molecules. The properties of the antigens are described and compared. The Mr 23,000 antigen is present on both testicular and cauda epididymidal spermatozoa, has a pI of 6.1, contains no detectable carbohydrate, is not tissue-specific and is degraded by V8 protease. By contrast, the 2D6 antigen is glycosylated, has a broad pI from 4.5 to 6.1, is tissue- and species-specific and is resistant to digestion with V8 protease. Its role in sperm-egg recognition is discussed.
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PMID:Identification and characterization of the 2D6 and Mr 23,000 antigens on the plasma membrane of rat spermatozoa. 243 64

A mouse monoclonal IgM antibody reactive with dendritic cells (DC) from the Brown Norway (BN) rat was prepared. This antibody (1F119) binds to a membrane-bound antigen present on DC from thoracic duct lymph, spleen, thymus, and lymph node. The antigen is present only in low density on 5% of splenic macrophages (M phi) and absent from peritoneal M luminal diameter. In situ, the antibody exhibits a strong reactivity towards DC in the thymic medulla, whereas no reaction is observed with cortical cells. Furthermore, cells positive for 1F119 can be identified in T-cell areas of spleen, lymph node, and Peyers' patches. 1F119 was genetically restricted in that a strong reactivity was found with DC from rats of the RT1n and RT1u haplotypes, an intermediate reactivity with the RT1c haplotype, only a weak reactivity with the RT1l and RT1b haplotypes, and no reactivity with the RT1a and RT1k haplotypes. The relatively weak reactivity of 1F119 with respect to the RT1l haplotype also appeared from a weak binding of 1F119 to DC from Lewis rats, as was assessed by FACS analysis. This result was comparable to the binding of OX3 (RT1.Bl and RT1.Bu) to DC from BN rats. Studies performed on thymus sections of recombinant rat strains indicate that 1F119, despite its apparent specificity for DC, reacts with a polymorphic RT1.B product.
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PMID:Recognition of rat dendritic cells by a monoclonal antibody. 244 81

Protein kinase activity of dark-adapted bovine rod outer segments is partitioned by centrifugation into soluble and membrane-bound fractions. The soluble kinases are separated by DEAE-cellulose chromatography into three peaks of activity, which can be classified by substrate specificity and cyclic nucleotide dependence into two categories. One peak of protein kinase activity has the characteristics reported for rhodopsin kinase (category one); it phosphorylates only bleached rhodopsin, and its activity is not affected by light, exogenous adenosine cyclic 3',5'--monophosphate (cAMP), guanosine cyclic 3',5'-monophosphate (cGMP), or a protein kinase inhibitor from skeletal muscle. Rhodopsin kinase has an apparent molecular weight of 68 000. The second category of kinase includes two peaks of activity which are stimulated severalfold by cAMP or cGMP but not by light. These protein kinases phosphorylate soluble proteins including histones and a protein kinase substrate prepared from rat intestine but not rhodopsin. The two peaks elute from DEAE-cellulose with 0.09 and 0.20 M KCl, suggesting that they are similar respectively to type I and type II cyclic nucleotide dependent protein kinases that have been characterized in other tissues. The activity of type I kinase is variable and much less than that of the type II enzyme; its molecular weight was not determined. The type II protein kinase has an apparent molecular weight of 165 000. This study confirms that different protein kinase enzymes catalyze selectively the phosphorylation of bleached rhodopsin and soluble proteins, and it repudiates the speculation in a previous publication [Farber, D. B., Brown, B. M., & Lolley, R. N. (1979) Biochemistry 18, 370-378] that a single protein kinase might catalyze both phosphorylation reactions.
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PMID:Protein kinases of retinal rod outer segments: identification and partial characterization of cyclic nucleotide dependent protein kinase and rhodopsin kinase. 627 85

Brown adipose tissue is an important site of cold-induced nonshivering thermogenesis in many mammals. The plasma membrane-bound Na+-K+-ATPase has been shown to be significantly involved in this thermogenesis although its exact role is unknown at present. Evidence that coupling of oxidative phosphorylation to electron transport may become loosened during thermogenesis has prompted an investigation of potential roles of the Na+-K+ pump that would be compatible with altered respiratory coupling. One such role is that of modulating norepinephrine (NE)-induced lipolysis and hence provision of free fatty acids to the mitochondria. Under such conditions, inhibition of the pump would reduce NE-induced respiration by limiting substrate availability. If, in fact, the primary role of the pump in NE-induced thermogenesis is to facilitate substrate availability, provision of exogenous substrate should bypass this involvement and ameliorate the ouabain inhibition of respiration. In the present study, this possibility was examined by determining the effect of an exogenous substrate, butyrate, on the contribution of the Na+-K+ pump to NE-stimulated respiration of isolated hamster brown adipocytes. Although exogenous butyrate was able to serve as a substrate for brown adipocyte respiration, its presence had no significant effect on the ouabain sensitivity of NE-induced rates of oxygen consumption. That is, ouabain (1 mM) inhibited the NE-evoked thermogenesis of the adipocytes by 77.7 +/- 6.5% in the absence of butyrate (2 mM) and by 73.4 +/- 9.9% in its presence. It appears, therefore, that the contribution of the Na+-K+ membrane pump to brown fat thermogenesis does not simply reflect modulation of NE-evoked lipolysis.
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PMID:Effects of butyrate on ouabain-sensitive respiration of hamster brown adipocytes. 705 78

Transfectants that express membrane-bound (MB) or secrete soluble truncated (TR) rat class I RT1.Aa major histocompatibility (MHC) antigens induce alloimmunity in vivo. The MB-RT1.Aa was produced by transfecting the full-length RT1.Aa cDNA, including the alpha 1, alpha 2, and alpha 3, transmembrane and intracellular domains. The TR-RT1.Aa cDNA insert included only the extracellular alpha 1, alpha 2, and alpha 3 domains; a stop codon was placed in front of the transmembrane domain. Following full-length sequencing, MB-RT1.Aa and TR-RT1.Aa cDNAs were translated in vitro into glycosylated MB-RT1.Aa (45 kDa) and TR-RT1.Aa (36 kDa) proteins, respectively. Each cDNA construct was individually subcloned into the pSG5 vector before transfection into Buffalo (BUF; RT1b) hepatoma cells. FACscan analysis with anti-RT1.Aa-specific R2/15S monoclonal antibody (MAb) confirmed surface expression of RT1.Aa molecules on the MB-RT1.Aa, but not on the TR-RT1.Aa, transfectants. In contrast, enzyme-linked immunoadsorbent assays documented the presence of soluble RT1.Aa molecules in supernates from cells transfected with the TR-RT1.Aa, but not from cells transfected with the MB-RT1.Aa, cDNA. Subcutaneous injection of MB-RT1.Aa or TR-RT1.Aa transfectants to BUF or Wistar Furth (WF; RT1u) rats induced accelerated rejection of ACI (RT1a) but not third-party Brown Norway (RT1n) heart allografts. Furthermore, supernates of TR-RT1.Aa, but not of MB-RT1.Aa, transfectants immunized WF hosts toward ACI hearts. Thus, both intact MB-RT1.Aa and soluble TR-RT1.Aa class I alloantigens induce potent sensitization against alloantigens.
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PMID:Membrane-bound or soluble truncated RT1.Aa rat class I major histocompatibility antigens induce specific alloimmunity. 757 Sep 58

In the presence of albumin Merocyanine 540 (MC540) exhibits a very limited binding to the outer surface of the membrane of normal erythrocytes, whereas pronounced binding is observed to leukemia cells. To find out whether this difference is due to differences in the composition or structural organization of the cell membrane we analyzed effects of a number of covalent and non-covalent perturbations of the red cell membrane on the binding and fluorescence characteristics of membrane-bound MC540. It is shown that exposure of the cells to cationic chlorpromazine, neuraminidase or photodynamic treatment with AlPcS4 as sensitizer caused a limited increase (30-50%) of MC540 binding, together with a red shift of the fluorescence emission maximum and an increase of the relative fluorescence quantum yield of membrane-bound MC540. Other forms of perturbation of the membrane structure, like hyperthermia (48 degrees C) and treatments that produce a decrease of phospholipid asymmetry in addition to accelerated flip-flop, did not result in increased MC540 binding, but did cause a red shift of the fluorescence emission maximum and an increase of the relative fluorescence quantum yield. These changes in fluorescence properties indicate a penetration of the dye into more hydrophobic regions in the membrane. MC540, bound to Brown Norway myelocytic leukemia cells, exhibited a red shift of the fluorescence emission maximum and an increased relative fluorescence quantum yield as compared to MC540 bound to untreated erythrocytes. These changes were of the same order of magnitude as in photodynamically treated red blood cells. Dye binding per surface area, however, was about 3-times higher with these leukemia cells than with photodynamically treated red blood cells. This demonstrates that certain perturbations of the erythrocyte membrane evoked a MC540 binding that became qualitatively comparable to the dye binding to leukemia cells, although dye binding per surface area was still significantly lower.
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PMID:Factors affecting the amount and the mode of merocyanine 540 binding to the membrane of human erythrocytes. A comparison with the binding to leukemia cells. 775 53

A previous study, in which a lysed fraction was used with endogenous phospholipids as substrate, revealed age-related changes in PA and PIP2 formation but not in PIP formation (Bothmer et al., Neurochem. Int. 21, 223-228, 1992). To rule out the influence of substrate availability in the present study, the effect of age on PI kinase, PIP kinase and DAG kinase activities was studied with exogenous phospholipids as substrate in the cerebral cortex from 8-month-old, 14-month-old and 26-month-old Brown Norway rats. PI kinase activity was predominantly located in a tight membrane-bound protein fraction, DAG kinase activity in cytosolic and loosely membrane-bound protein fractions, and PIP kinase activity was present in all three protein preparations. The effects of age were limited to a small increase in kinase activity in the tight membrane-bound protein fraction in 14-month-old and 26-month-old rats compared to 8-month-old rats, and a 10% decrease in PIP kinase activity in the cytosolic protein fraction in 14-month-old and 26-month-old rats compared to 8-month-old rats. DAG kinase activity showed no age-related changes. In conclusion, one should take care in comparing rat aging with human aging as PI kinase activity shows an age-related decline in human brain cortex (Jolles et al., J. Neurochem. 58, 2326-2329, 1992). Furthermore, previously reported decreases in PA formation rates in rat brain are probably not due to changes in DAG kinase itself but to changes in DAG availability, although further experimental evidence is needed to confirm this conclusion.
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PMID:The effect of age on phosphatidylinositol kinase, phosphatidylinositol phosphate kinase and diacylglycerol kinase activities in rat brain cortex. 792 21

The hydropathy plot of the inwardly rectifying ROMK1 K+ channel, which reveals two transmembrane and a pore region domains, also reveals areas of intermediate hydrophobicity in the N terminus (M0) and in the C terminus (post-M2). Peptides that correspond to M0, post-M2, and a control peptide, pre-M0, were synthesized and characterized for their structure, affinity to phospholipid membranes, organizational state in membranes, and ability to self-assemble and coassemble in the membrane-bound state. CD spectroscopy revealed that both M0 and post-M2 adopt highly alpha-helical structures in 1% SDS and 40% TFE/water, whereas pre-M0 is not alpha-helical in either 1% SDS or 40% TFE/water. Binding experiments with NBD-labeled peptides demonstrated that both M0 and post-M2, but not pre-M0, bind to zwitterionic phospholipid membranes with partition coefficients of 10(3)-10(5) M-1. A surface localization for both post-M2 and M0 was indicated by NBD shift, tryptophan quenching experiments with brominated phospholipids, and enzymatic cleavage. Resonance energy transfer measurements between fluorescently labeled pairs of donor (NBD)/ acceptor (rhodamine) peptides revealed that M0 and post-M2 can coassemble in their membrane-bound state, but cannot self-associate when membrane-bound. The results are in agreement with recent data indicating that amino acids in the carboxy terminus of inwardly rectifying K+ channels have a major role in specifying the pore properties of the channels (Taglialatela M, Wible BA, Caporaso R, Brown AM, 1994 Science 264:844-847; Pessia M, Bond CT, Kavanaugh MP, Adelman JP, 1995, Neuron 14:1039-1045). The relevance of the results presented herein to the suggested model for the structure of the ROMK1 channel and to general aspects of molecular recognition between membrane-bound polypeptides are also discussed.
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PMID:Secondary structure, membrane localization, and coassembly within phospholipid membranes of synthetic segments derived from the N- and C-termini regions of the ROMK1 K+ channel. 893 Nov 47

We have investigated the effect of UVC irradiation on "TGF alpha ase" activity using both intact HeLa cells and isolated membrane fragments with an assay based on the previously described nonapeptide substrate method [Brown et al. (1992): J Cell Biochem 48:411-423]. This method allows recognition of cleavage at the scissile bond cognate with that of the TGF alpha N-terminal cleavage site from its membrane-bound precursor. The level of ectoendopeptidase (including "TGF alpha ase") activity observed on intact cells was lower than that of ectoaminopeptidases. Addition of foetal bovine serum (FBS) enhanced aminopeptidase and dipeptidyl peptidase activity but inhibited "TGF alpha ase" activity, while phorbol 12-myristate 13-acetate (PMA) had no significant effect on the ectopeptidases monitored, expect for "TGF alpha ase," which was also inhibited, in contradistinction to their effects in other cell systems. Sublethal UVC irradiation (10 Jm-2) of the cultures resulted in activation of the ectoaminopeptidase and ectoendopeptidases which was maximal 16 and 20-24 h after irradiation, respectively. The addition of FBS to these irradiated cells appeared to reduce the increase in endopeptidase products, due in part to increased aminopeptidase activity but also to the direct inhibitory effect of FBS on the "TGF alpha ase." The activation of these proteases by UVC, even at high fluences (500 Jm-2), was not observed within the first 30 min after the cells were irradiated. Purified plasma membrane fragments were prepared from suspension cultures of HeLa cells and displayed high levels of "TGF alpha ase" activity. The rate of "TGF alpha ase" activity using 140 nM peptide substrate (P9) was 5.6 pmol/min/mg membrane protein, which was elevated to 13.7 pmol/min/mg membrane protein, 20 h after the cells had been irradiated with 10 Jm-2 UVC. Inhibition studies indicate that the plasma membrane "TGF alpha ase is a metalloenzyme as it was inhibited by EDTA, EGTA, and 1,10-phenanthroline but not by elastase or serine protease inhibitors. "TGF alpha ase" activity on intact cells was shown to be inhibited by 1,10-phenanthroline, which further supports this suggestion. Treatment of the membranes with Triton X-100 resulted in a loss of "TGF alpha ase" activity, raising the possibility that this enzyme may require a cofactor to be fully functional. We show that in purified membrane preparations of HeLa cells there is evidence for the presence of a "TGF alpha ase" which can be activated by UV irradiation, which differs from the putative "TGF alpha ase" described in various other cell lines, and which does not seem dependent on protein kinase C (PKC) activity.
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PMID:UVC activation of the HeLa cell membrane "TGF alpha ase," a metalloenzyme. 905 93


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