共查询到20条相似文献,搜索用时 31 毫秒
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Harold Koenig Alfred Goldstone Chung Y. Lu 《Biochemical and biophysical research communications》1982,106(2):346-353
Testosterone induced a rapid (<1 min) stimulation of endocytosis, amino acid and hexose transport, measured by the temperature-sensitive uptake of HRP, 14C-AIB and 3H-DG, in mouse kidney cortex slices. The hormonal increment in uptake persisted for at least 60–120 min, showed time-, energy-, and Na+-dependence, and varied with substrate and testosterone concentration. Testosterone was maximally effective at 10?8 to 10?7 M. Peroxidase histochemistry indicated that the hormonal increase in HRP uptake is restricted to proximal tubules. Testosterone was more effective than DHT, whereas cyproterone acetate, androsterone and dexamethasone had little or no stimulating effect on this uptake. Kidney slices from androgen-insensitive mice did not respond to testosterone. The rapid increase in endocytosis, amino acid and hexose transport may represent a direct, receptor-mediated response of the surface membrane of target cells to testosterone. 相似文献
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A template independent poly (A)·poly (U) synthesizing activity has been isolated from . This activity is eluted from a DNA-cellulose column along with DNA-dependent RNA polymerase. The column fractions which exhibit this activity contain RNA polymerase holoenzyme plus a polypeptide which is slightly larger than sigma factor; pure RNA polymerase holoenzyme did not synthesize poly (A)·poly (U). The activity was dependent on the presence of ATP, UTP, and Mn++ (Mg++ could not substitute), and was inhibited by rifampicin, streptolydigin, and Cibacron Blue. The incorporation of nucleotides was not linear with time, but appeared after a lag period. The results suggest that a modified form of DNA-dependent RNA polymerase analogous to holoenzyme II is catalyzing the synthesis of poly (A)·poly (U). 相似文献
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DNA-free minicells of will not allow growth of phage T-7, nor is RNA synthesis stimulated by phage infection. Thus, these miniature cells seem not to contain RNA polymerase activity. However, DNA-dependent RNA polymerase activity can be unmasked in extracts with poly(dA-T) and Mn2+. This activity may represent a cytoplasmic pool of inactive RNA polymerase in normal cells. 相似文献
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Antigenic homology of eukaryotic RNA polymerases 总被引:6,自引:0,他引:6
C J Ingles 《Biochemical and biophysical research communications》1973,55(2):364-371
Facilitated by an improved enzyme purification procedure, antisera to calf thymus DNA-dependent RNA polymerase II was prepared in hens. Using immunoprecipitation and inhibition of enzymatic activity the immunological properties of several eukaryotic RNA polymerases were examined. Purified calf thymus and rat liver polymerase II exhibited antigenic homology. The partially purified amphibian () and protozoan () polymerase II had reduced crossreactivities. Calf thymus polymerase I also shared antigenic homology with the form II enzymes. 相似文献
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Seung-ki Lee Richard A. Jungmann 《Biochemical and biophysical research communications》1981,102(1):538-544
The phosphorylation of RNA polymerase II after isoproterenol stimulation of confluent rat C6 glioma cell cultures has been investigated. Glioma cells were incubated in the presence of Na2H32PO4 and stimulated for 1 hour with the β-adrenergic agonist isoproterenol. The phosphorylation pattern was analyzed after purification of RNA polymerase II by immunoprecipitation, SDS-polyacrylamide gel electrophoresis and autoradiography. Isoproterenol markedly increased [32P]phosphate incorporation into the 214,000 dalton RNA polymerase subunit. Analysis of the phosphate acceptor amino acid revealed the presence of only [32P]phosphoserine. The data demonstrates an isoproterenol-induced structural modification of RNA polymerase II. 相似文献
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Stuart L. Marcus Gregg Lipschik Generosa Trueba Cyrus J. Bacchi 《Biochemical and biophysical research communications》1980,93(4):1027-1035
A single peak of DNA polymerase activity from extracts of , obtained by DEAE-cellulose and phosphocellulose ion-exchange chromatography, was resolved into two peaks differing in KCl concentration necessary to elute them from a DNA-agarose column. Peak I (eluting at 0.2 M KCl) and Peak II (eluting at 0.4 M KCl), differed in response to increasing KCl concentrations, although both functioned optimally with Mg2+ as divalent cation when DNA synthesis was directed either by activated DNA or poly (dC)·(dG)12–18. Due to the potential significance of polyamines in the metabolism of , the effect of exogenous polyamine on rates of DNA synthesis by the peak I and II enzymes was compared with that of murine DNA polymerase alpha. Only the peak I enzyme was significantly stimulated (up to 4-fold) by the biologically active polyamines spermine and spermidine at physiological concentrations. The response of the peak I enzyme resembled that of the alpha polymerase. This result suggests a possible functional difference between peak I and II enzymes, as well as a potential target site for trypanocidal drug development. 相似文献
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K H Falchuk L Ulpino B Mazus B L Vallee 《Biochemical and biophysical research communications》1977,74(3):1206-1212
DNA dependent RNA polymerase I has been purified to homogeneity. α-amanitin, over the concentration range 0.05 to 200 μg/ml, does not affect its activity, consistent with its being classified as an RNA polymerase I. Based on a molecular weight of 624,000 daltons the enzyme contains 2.2 g atom of Zn but no Mn, Cu, Fe, as determined by microwave excitation emission spectrometry. Zinc is essential for activity since the chelating agent, 1,10-phenanthroline, inhibits enzymatic function but its non-chelating analogue, 4,7-phenanthroline is ineffective. Thus, like the RNA polymerase II, zinc is a catalytically essential component of RNA polymerase I (1). 相似文献
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The effects of strain, sex, hypophysectomy and hormone treatment on mouse submandibular gland renin, kallikrein, S2266 hydrolase, and BAEe esterase activities have been examined. Renin activity is determined by the locus on mouse Chromosome 1. Female SWR/J mice (/) have 1000-fold higher submandibular gland renin activity than C57BL/6J mice (/). Both strains have similar kallikrein activity. Renin, BAEe esterase, and S2266 hydrolase are substantially higher in male mice compared to females of the same strain whereas kallikrein is not. Dihydrotestosterone and/or thyroxine treatment induces renin, BAEe esterase, and S2266 hydrolase in female mice with little effect on kallikrein. All four enzyme activities are profoundly reduced by hypophysectomy. Dihydrotestosterone and thyroxine are both required to restore renin, BAEe esterase, and S2266 hydrolase to induced levels. Dihydrotestosterone and.or thyroxine restores kallikrein to control levels. We conclude that renin and kallikrein in the mouse submandibular gland are under different genetic and endocrine control. In addition, the synthetic substrate S2266 is not a specific substrate for kallikrein activity in mouse submandibular gland cytosol. 相似文献