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31.
Hepatitis C virus core protein interacts with the cytoplasmic tail of lymphotoxin-beta receptor. 总被引:22,自引:2,他引:20
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M Matsumoto T Y Hsieh N Zhu T VanArsdale S B Hwang K S Jeng A E Gorbalenya S Y Lo J H Ou C F Ware M M Lai 《Journal of virology》1997,71(2):1301-1309
Hepatitis C virus (HCV) core protein is a multifunctional protein. We examined whether it can interact with cellular proteins, thus contributing to viral pathogenesis. Using the HCV core protein as a bait to screen a human liver cDNA library in a yeast two-hybrid screening system, we have isolated several positive clones encoding cellular proteins that interact with the HCV core protein. Interestingly, more than half of these clones encode the cytoplasmic domain of lymphotoxin-beta receptor (LT betaR), which is a member of the tumor necrosis factor receptor family. Their binding was confirmed by in vitro glutathione S-transferase fusion protein binding assay and protein-protein blotting assay to be direct and specific. The binding sites were mapped within a 58-amino-acid region of the cytoplasmic tail of LT betaR. The binding site in the HCV core protein was localized within amino acid residues 36 to 91 from the N terminus, corresponding to the hydrophilic region of the protein. In mammalian cells, the core protein was found to be associated with the membrane-bound LT betaR. Since the LT betaR is involved in germinal center formation and developmental regulation of peripheral lymphoid organs, lymph node development, and apoptotic signaling, the binding of HCV core protein to LT betaR suggests the possibility that this viral protein has an immunomodulating function and may explain the mechanism of viral persistence and pathogenesis of HCV. 相似文献
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34.
The effect of an applied electromagnetic field on drug diffusion in a one dimensional, three-layer drug-receptor model has
been analyzed and expressed in terms of a normalized turnover rate parameter. The analysis reveals that an imposed harmonic
time-varying electromagnetic field may enhance or retard the drug turnover rate depending on the diffusional pattern, the
equivalent Michaelis constant, the maximum drug turnover rate of the intrinsic drug-receptor system, as well as the power
density and frequency of the applied electromagnetic field. It is estimated that the power density in the order of magnitude
of 1μW/cm2 at 100 MHz frequency range may be required to induce significant rate effects. 相似文献
35.
A microbial cooxidation process for 1,2-dihydroxy-1,2-dihydronaphthalene from naphthalene has been demonstrated. A Pseudomonas putida it119 mutant strain grown with glucose as the sole carbon and energy source was used to oxidize naphthalene. Growth characteristics of the P. putida mutant strain were studied in both batch and continuous fermentation experiments. The rate of product formation was found to depend on naphthalene particle sizes, initial naphthalene and glucose concentrations. Kinetic models were developed to quantify the microbial cooxidation process and a two-stage fermentation process is proposed for further studies. 相似文献
36.
A relatively stable enzyme system that converts versiconal hemiacetal acetate to versicolorin A was isolated from the soluble fraction of the homogenized cells of Aspergillus parasiticus ATCC 15517. The cell-free preparation did not require oxygen or oxidized nicotinamide adenine dinucleotide phosphate for activity, nor did it require dithiothreitol, polyclar (polyvinyl pyrrolidone), or glycerol for stabilization of activity. It was susceptible to inhibition by dichlorvos and cysteine. Isotope tracer studies revealed involvement of several intermediates in the conversion of versiconal hemiacetal acetate to versicolorin A. These findings confirm the biogenetic relationship of versiconal hemiacetal acetate and versicolorin A, and they confirm that the bisfuran ring structure in aflatoxins and related fungal metabolites is derived from the hemiacetal structure of versiconal hemiacetal acetate. 相似文献
37.
The range of phenylalanine hydroxylase activity was determined by measuring the conversion of radioactive phenylalanine to tyrosine in liver and kidney of various vertebrates. Rodents (rats, mouse, gerbil, hamster and guinea pig) were found to have the highest liver phenylalanine hydroxylase activity among all animals studied. They are also the only species that possessed a significant kidney phenylalanine hydroxylase activity which was about 25% of that found in the liver of the same animal. The synthetic dimethyl-tetrahydro-pteridine, used as a cofactor for the enzyme assay in most studies, catalyzed non-enzymatic hydroxylation of phenylalanine to tyrosine. Inclusion of boiled-blank and strict control of timing between incubation and product measurement were essential precautions to minimize erroneous results from substrate contamination and non-enzymatic hydroxylation. 相似文献
38.
A continuous-culture device was used to select and enrich for microorganisms, from sewage and agricultural runoff, that were capable of using the organophosphorus insecticide parathion as a sole growth substrate. Parathion was dissimilated by the highly acclimated symbiotic activities of Pseudomonas stutzeri, which non-oxidatively and cometabolically hydrolyzed the parathion to ionic diethyl thiophosphate and p-nitrophenol, and P. aeruginosa, which utilized the p-nitrophenol as a sole carbon and energy source. Ionic diethyl thiophosphate was found to be inert to any transformations. Methyl parathion was dissimilated in an analogous way. The device functioned as a chemostat with parathion as the growth-limiting nutrient, and extraordinarily high dissimilation rates were attained for parathion (8 g/liter per day) and for p-nitrophenol (7 g/liter per day). This is the first report of parathion utilization by a defined microbial culture and by symbiotic microbial attack and of dissimilation of an organophosphorus pesticide in a chemostat. 相似文献
39.
A trypsin inhibitor (ACTI) was isolated and purified from the seeds of Acacia confusa by gel filtration, and trypsin-Sepharose 4B column affinity chromatography. The molecular weight of ACTI was found to be 21,000 +/- 1,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and amino acid composition analysis. ACTI contained four half-cystine and no methionine residues, and was rich in aspartic acid, glutamic acid, glycine, leucine, and lysine residues. The native trypsin inhibitor was composed of two polypeptide chains, and it inhibited trypsin and alpha-chymotrypsin stoichiometrically at the molar ratio of 1:1 and 2:1, respectively. The amino-terminal sequence analysis of the A. confusa trypsin inhibitor A and B chains revealed a more extensive homology with Acacia elata and silk tree trypsin inhibitors, and a less extensive homology with Kunitz soybean trypsin inhibitor. 相似文献
40.
Homozygous tyrosinase gene mutation in an American black with tyrosinase-negative (type IA) oculocutaneous albinism 总被引:5,自引:2,他引:3
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R A Spritz K M Strunk C L Hsieh G S Sekhon U Francke 《American journal of human genetics》1991,48(2):318-324
We have identified a tyrosinase gene mutation in an American black with classic, tyrosinase-negative oculocutaneous albinism. This mutation results in an amino acid substitution (Cys----Arg) at codon 89 of the tyrosinase polypeptide. The proband is homozygous for the substitution, suggesting that this mutation may be frequently associated with tyrosinase-negative oculocutaneous albinism in blacks. 相似文献