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61.
Karol Mičieta 《Folia Geobotanica》1983,18(3):329-331
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N G Ahn R Seger R L Bratlien C D Diltz N K Tonks E G Krebs 《The Journal of biological chemistry》1991,266(7):4220-4227
Epidermal growth factor stimulates the activity of several cytosolic serine/threonine protein kinases in quiescent Swiss 3T3 cells. Two of these, which use myelin basic protein (MBP) as substrate, act as kinase kinases in that they are able to activate a separate peptide kinase activity in vitro by a mechanism involving protein phosphorylation. In this study, we have identified two activities from extracts of epidermal growth factor-treated cells that stimulate an ATP-dependent activation of both of the MBP kinases, derived in their inactive precursor forms from extracts of untreated cells. The resulting MBP kinase activities are stable to further purification and can be inactivated with either tyrosine or serine/threonine protein phosphatases and then reactivated to their original levels of activity. Thus, we propose that the in vitro activation involves protein phosphorylation, stimulated by the action of novel MBP kinase activating factors that represent intermediate components in a growth factor-stimulated kinase cascade. 相似文献
64.
BVDV(牛病毒性腹泻病毒)是一类有重要经济价值的病毒,其核酸为单链RNA。该病毒提纯以后.用苯酚-氯仿-异戊醇提取RNA.在提取的BVDy RNA中所含的DNA杂质用DNase I降解除去,然后进一步用oligo dT纤维素拄亲和层析,琼脂糖凝胶电泳等方法纯化。纯化的BVDV RNA在E.coli,poly A聚合酶的催化作用下,在3’羟基末端聚腺化。cDNA在逆向转录酶的作用下,用polyA接尾的BVDV RNA作模板,oligodT_12—18作引物合成。琼脂糖凝胶电泳结果说明它与BVDV RNA相似。该cDNA的探针用斑点杂交方法与BVDV RNA,HCV RNA和酵母tRNA杂交,BVDV RNA和HCVRNA显阳性反应,酵母tRNA显阴性反应,结果说明合成的cDNA为BVDV RNA的cDNA。BVDV和HCV同为披盖科疫病毒属成员,它们具有部分相同的抗原,因此编码病毒蛋白的RNA序列具有同源序列,本研究证实了这种假设。 相似文献
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Kinetic properties of a L-cysteine desulfhydrase-deficient mutant in the enzymatic formation of L-cysteine from D,L-ATC 总被引:1,自引:0,他引:1
Summary A mutant strain lacking in activity of L-cysteine desulfhydrase, a L-cysteine-decomposing enzyme, was screened after UV-treatment ofPseudomonas sp. CU6. The properties of the two strains, original and mutant, were compared on the basis of parameter values estimated from kinetic simulations of the enzymatic formation of L-cysteine from D,L-ATC. Both strains suffered from product inhibition, though inhibition was less for the mutant strain. 相似文献
68.
Summary The cloning of glucoamylase geneSTA using theSUC2 promoter intoSaccharomyces cerevisiae was performed. The signal sequence ofSTA gene was used for the secretion of glucoamylase protein. The plasmid constructed in this way was named YEpSUCSTA and its expression was identified. The expression of YEpSUCSTA was repressed in the presence of glucose in growth medium, but derepressed when glucose became depleted. YEpSUCSTA showed the similar efficiency of glucoamylase secretion as YEpSTA-F which has the entireSTA gene. Glucoamylase activity in starch-glucose medium was largely increased because cell mass and plasmid stability were high in biosynthesis phase compared to extracellular glucoamylase activities in media which starch or glucose was the only carbon source. 相似文献
69.
Ammonium ingestion prevents depletion of hepatic energy metabolites induced by acute ammonium intoxication 总被引:1,自引:0,他引:1
E Kosenko V Felipo M D Mi?ana E Grau S Grisolía 《Archives of biochemistry and biophysics》1991,290(2):484-488
Ingestion of an ammonium containing diet produces hyperammonemia and protects rats against acute ammonium intoxication. Acute ammonium toxicity has been attributed to the depletion of energy metabolite intermediates. We show here that hyperammonemia affords considerable protection against depletion of hepatic energy metabolites evoked by ammonium acetate injection. In control rats there were marked decreases in the content of acetoacetate, beta-hydroxybutyrate, ATP, 2-oxoglutarate, lactate, and pyruvate while phosphoenolpyruvate increased markedly. In hyperammonemic rats beta-hydroxybutyrate, ATP, 2-oxoglutarate, and lactate were not significantly affected while pyruvate increased markedly and phosphoenolpyruvate slightly. These results suggest that in controls the activity of pyruvate kinase is inhibited after ammonium injection while in hyperammonemic rats it is not inhibited. The content of alanine (an inhibitor of pyruvate kinase) reached 2.8 mumol/g in controls and 1.6 mumol/g in hyperammonemic rats, 15 min after ammonium injection. This could explain the different effects of ammonium injection on control and hyperammonemic rats. 相似文献
70.
Summary An inherited (maternal origin) 13/14 translocation with the nucleolus organizer regions eliminated and one centromere was found in an oligospermic man whose wife had had two spontaneous abortions. Meiotic studies revealed all stages of spermatogenesis with a trivalent configuration in diakinesis. Possible reasons for his subfertility and his mother's normal fertility are discussed. 相似文献