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Bernhard J. Eikmanns Manfred Kircher Dieter J. Reinscheid 《FEMS microbiology letters》1991,82(2):203-208
Different strains of Corynebacterium glutamicum, Brevibacterium flavum, and Brevibacterium lactofermentum were analysed for restriction fragment length polymorphism using the homoserine dehydrogenase gene (hom) as a probe. The hybridization patterns obtained PvuII- or Asp700-restriction of chromosomal DNA were specific and distinguishable for each of the three species and identical for the different strains of each species. Thus, the method employed allows rapid distinction of Corynebacterium glutamicum, Brevibacterium flavum, and Brevibacterium lactofermentum. The former species could also be discriminated from the latter two by its resistance to 0.5 g/l of the methionine analog ethionine. 相似文献
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Degradation of abnormal proteins in Bacillus megaterium and Saccharomyces cerevisiae in vivo was compared with that in cell-free extracts. Protein degradation in vivo, when the cells were labelled with 14C-leucine during growth in the presence of ethionine, was affected by the concentration of the analogue used. Proteins synthesized in the presence of 0.2–1 mM ethionine were degraded most rapidly in both organisms. The proteolytic enzyme system of yeast degraded the analogue-containing proteins in vitro faster than the normal proteins. This holds also for proteins synthesized in the presence of 5 mM ethionine, whose degradation in vivo was impaired. The proteolytic system of B. megaterium, on the other hand, was unable in vitro to differentiate between normal and abnormal proteins. Denatured proteins underwent preferential degradation over normal and ethionine-containing proteins.Participant in the UNESCO Postgraduate Course On Modern Problems in Biology and Microbial Technology. 相似文献
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Yoshizawa F Watanabe E Sugahara K Natori Y 《Biochemical and biophysical research communications》2002,298(2):235-239
Administration of ethionine to female rats is known to inhibit hepatic protein synthesis by reducing the level of hepatic ATP. Administration of methionine and/or adenine rapidly restores the ATP levels and protein synthesis. The ethionine administration causes a progressive disaggregation of hepatic polysomes, suggesting that the initiation step of protein synthesis is inhibited. Recent studies indicate that changes in initiation are associated with alterations in the phosphorylation states of translational initiation regulators such as eukaryotic initiation factor (eIF) 4E, eIF4E-binding protein 1 (4E-BP1), and the 70-kDa ribosomal protein S6 kinase (S6K1). We found that these initiation regulators are hypophosphorylated in rat liver during ethionine-mediated ATP depletion (60% of the control value). Furthermore, the restoration of the ATP levels by the administration of methionine and adenine brought about a complete recovery of the phosphorylation states of all these regulators. The present data suggest that hypophosphorylation of various initiation regulators represents the primary event in the ethionine-induced breakdown of polysomes and inhibition of protein synthesis in the liver. Possible involvement of mammalian target of rapamycin (mTOR), as a sensor of intracellular ATP level, was also discussed. 相似文献
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Yoshiaki Takahashi Kikuo Ogata 《Biochimica et Biophysica Acta (BBA) - Gene Structure and Expression》1982,697(1):101-112
The inhibitory effects of ethionine treatment of female rats for 4 h on the protein-synthesizing machineries of 80 S ribosomes and 40 S ribosomal subunits of the liver were investigated. The following results were obtained. (1) The translation of globin mRNA by 80 S ribosomes or 40 S ribosomal subunits, in combination with mouse 60 S subunits, was markedly inhibited by ethionine treatment in a complete cell-free system containing partially purified initiation factors of rabbit reticulocytes and the rat liver pH 5 fraction. (2) The polysome formation of 80 S ribosomes in the complete system described above was inhibited by ethionine treatment. Similar inhibitions by ethionine treatment were observed in the case of incubation of 40 S subunits with reticulocyte lysate, although the polysome formation was rather low even in the case of control 40 S subunits. (3) The pattern of CsCl isopycnic centrifugation of rat liver native 40 S subunits uniformly labeled with [14C]- or [3H]orotic acid showed that the content of non-ribosomal proteins of native 40 S subunits was decreased by ethionine treatment. The analysis of proteins of native 40 S subunits by SDS-polyacrylamide slab gel electrophoresis revealed that eIF-3 subunits and two unidentified protein fractions of molecular weight of 2.3·104 and 2.1·104 were decreased in ethionine-treated rat liver. (4) 40 S subunits from ethionine-treated or control rat livers were labeled with or , and the 3H to 14C ratios of individual 40 S proteins on two-dimensional polyacrylamide gel electrophoresis were measured. The results suggested that the conformation of rat liver 40 S subunits was changed by ethionine treatment. (5) These results may indicate that ethionine treatment decreases the activity of rat liver 40 S subunits for the interaction with initiation factors, especially eIF-3, as the results of conformational changes of 40 S subunits. 相似文献
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Elizabeth Clayton Stuart J. Forbes 《Biochemical and biophysical research communications》2009,381(4):549-1976
The intra-hepatic population of liver progenitor cells expands during liver injury when hepatocyte proliferation is inhibited. These cells can be purified by density gradient centrifugation and cultured. Separated by size only this population contains small cells of hematopoietic, epithelial and endothelial lineages and is thought to contain liver stem cells. The identity of liver stem cells remains unknown although there is some evidence that tissue Sca1+ CD45− cells display progenitor cell characteristics. We identified both intra-hepatic and gall bladder Sca1+ cells following liver injury and expanded ex vivo Sca1 cells as part of heterogenous cell culture or as a purified population. We found significant difference between the proliferation of Sca-1 cells when plated on laminin or collagen I while proliferation of heterogenous population was not affected by the extracellular matrix indicating the necessity for culture of Sca1+ cells with laminin matrix or laminin producing cells in long term liver progenitor cell cultures. 相似文献
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Abstract Monic acid A was isolated from a Pseudomonas fluorescens fermentation in which pseudomonic acid A (PA) was the principal secondary metabolite. [3-14 C]3-Hydroxy-3-methyl-glutaric acid (HMG) given early in the idiophase radiolabelled PA (1.1% incorporation), confirming experimentally the putative direct involvement of HMG in the biosynthesis of PA, but contributed relatively insignificant radiolabel to the monic acid extracted from the broth at the end of the fermentation. Ethionine inhibited (80%) PA biosynthesis and correspondingly reduced incorporation of [14 C]HMG. In contrast, ethionine increased incorporation of [methyl-14 C]methionine into PA and enhanced specific radioactivity of the antibiotic 8-fold. Ethionine inhibition of secondary metabolite methylations did not divert pseudomonate biosynthesis to give unusual analogues, implying that methylation of a putative pentaketide precursor of the monate moiety forms a vital intermediate of the pseudomonate pathway, but caused a new [14 C]HMG-derived polar metabolite of biosynthetic interest to become evident. 相似文献
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