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121.
A 250-kilodalton cellular protein is induced by progestins in two human breast cancer cell lines MCF7 and T47D 总被引:1,自引:0,他引:1
We have studied the effect of R5020, a synthetic progestin, on the biosynthesis of cellular proteins extracted from the MCF7 and T47D human breast cancer cells, using gel electrophoresis. R5020 stimulates the synthesis, as measured after [35S]-methionine labelling, and the accumulation, as shown by silver staining, of a protein of molecular weight approximately equal to 250,000. The increase of the labelled 250-kilodalton protein was rapid (3 hours) and after 3 days this protein represented approximately equal to 6% of the total cellular proteins (approximately equal to 1 microgram/150,000 cells). The induction of the 250-kilodalton protein was obtained by physiologically active concentrations of several progestins and high concentrations of 5 alpha-dihydrotestosterone but not by estradiol or dexamethasone. It was inhibited by R486 , a progestin antagonist, but not by flutamide, an androgen antagonist. These results indicate a mediation by the progesterone receptor. The 250-kilodalton protein appears to be an excellent probe to study in cell culture the mechanism of action of progestin on human cells. 相似文献
122.
Rabbit heart mitochondria were used as a source of enzymes for the synthesis of phosphoruslabeled creatine phosphate. This method is based on the coupled reaction between mitochondrial oxidative phosphorylation and mitochondrial-bound creatine kinase. It is possible to convert more than 90% of the inorganic phosphate (Pi) to creatine phosphate. The method used only small amounts of adenine nucleotides which led to a product with only slight nucleotide contamination. This could be removed by activated charcoal extraction. For further purification, a method for the removal of residual Pi is described. 相似文献
123.
Changes in key regulatory enzymes of hepatic carbohydrate metabolism after glucose loading of starved rats 总被引:5,自引:0,他引:5
T H Claus F Nyfeler H A Muenkel M G Burns T Pate S J Pilkis 《Biochemical and biophysical research communications》1984,125(2):655-661
When glucose was given to starved rats there was an increase in both 6-phosphofructo 2-kinase and pyruvate kinase activity and a decrease in fructose 2,6-bisphosphatase activity 30 min and 60 min later. These changes were accompanied by an increase in glycogen deposition and by modest, but significant increases in fructose 2,6-bisphosphate levels at the same time. Metabolite measurements indicated that flux through 6-phosphofructo 1-kinase and pyruvate kinase were increased. These results suggest that although glycogen deposition may occur via the gluconeogenic pathway, glycolysis is activated at the same time by changes in the phosphorylation state of key regulatory enzymes as well as by the small rise in fructose 2,6-bisphosphate. 相似文献
124.
Salvatore Passarella Anna Atlante Maria Barile Ernesto Quagliariello 《Biochemical and biophysical research communications》1984,121(3):770-778
GABA added to rat brain mitochondria causes oxidation of intramitochondrial NAD(P)H as well as inducing glutamate efflux from the mitochondrial matrix. The rate of NAD(P)H oxidation shows saturation characteristics, depends on GABA transport across the mitochondrial membrane and is inhibited by non-penetrant compounds and by the metal-complexing agent bathophenanthroline. These results show the existence of a specific GABA carrier. Inhibition studies strongly suggest the existence of two separate binding sites, namely the GABA binding site and the dicarboxylates binding site, as well as suggest the presence of a metal ion (ions) at GABA binding site. The occurrence of a GABA/GLUTAMATE antiport is proposed which allows a cyclical route to account for GABA synthesis and degradation in brain. 相似文献
125.
Fructose 2,6-bisphosphate, sugar phosphates and adenine nucleotides in the regulation of glucose metabolism in the lactating rat mammary gland 总被引:2,自引:0,他引:2
Fructose 2,6-bisphosphate is present in the rat mammary gland, rising from a value of 1.4 nmol/g in pregnancy to 4.3 nmol/g tissue at 14 days lactation; the equivalent values calculated/ml intracellular water are 5.2 and 11.6 nmol, respectively. The tissue content of fructose 6-phosphate, fructose 1,6-bisphosphate, ATP and phosphoenolpyruvate remain relatively constant in the transition from pregnancy to the height of lactation. The changes in AMP, cyclic AMP, and citrate content of the mammary gland during lactation are such as to promote an increase in fructose 2,6-bisphosphate formation and flux through phosphofructokinase. 相似文献
126.
Inositol trisphosphate, when added to permeabilized rat fat cells, led to a several-fold increase of pyruvate dehydrogenase activity due to conversion of the inactive phospho form (PDHb) to the active, dephospho form (PDHa). It is suggested that inositol trisphosphate, probably through intracellular Ca2+-mobilisation, acts as a physiological mediator of insulin for activation of the mitochondrial PDH-complex. 相似文献
127.
Lectin-like binding of Bacillus thuringiensis var. kurstaki lepidopteran-specific toxin is an initial step in insecticidal action 总被引:15,自引:0,他引:15
The two delta-endotoxins comprising the Bacillus thuringiensis var. kurstaki HD1 insecticidal protein crystal were separated. The lepidopteran-specific protoxin was activated in vitro and its mechanism of action investigated. Toxicity towards Choristoneura fumiferana CF1 cells was specifically inhibited by preincubation of the toxin with N-acetylgalactosamine and N-acetylneuraminic acid. The lectins soybean agglutinin and wheat germ agglutinin, which bind N-acetylgalactosamine, also inhibited toxicity. Since N-acetylneuraminic acid is not known to occur in insects, these results suggest that the toxin may recognise a specific plasma membrane glycoconjugate receptor with a terminal N-acetylgalactosamine residue. 相似文献
128.
Microbial mineralization of organic phosphate in soil 总被引:35,自引:0,他引:35
Summary Phosphate-dissolving microorganisms were isolated from non-rhizosphere and rhizosphere of plants. These isolates included
bacteria, fungi and actinomycetes. In broth cultures, Gram-negative short rod,Bacillus andStreptomyces species were found to be more active in solubilizing phosphate thanAspergillus, Penicillium, Proteus, Serratia, Pseudomonas andMicrococcus spp. The sterile soils mixed with isolated pure culture showed slower mineralization of organic phosphate than that of non-sterile
soil samples at all incubation periods. Maximum amount of phosphate mineralization by isolated microorganisms were obtained
at the 60th and the 75th day of incubation in sterile and non-sterile soils respectively. The mixed cultures were most effective
in mineralizing organic phosphate and individuallyBacillus sp. could be ranked next to mixed cultures. Species ofPseudomonas andMicrococcus were almost the same as that of the control under both sterile and non-sterile conditions. 相似文献
129.
John A. Cidlowski 《Biochimica et Biophysica Acta (BBA)/General Subjects》1984,800(3):258-268
Previous studies have demonstrated that the vitamin pyridoxal phosphate can alter the physicochemical properties of glucocorticoid receptors. We now report the localization of a pyridoxal phosphate binding site within the mero-receptor domain of this glucocorticoid receptor. Mero-glucocorticoid receptors that are generated by trypsin (10 μg/ml) or chymotrypsin (100 μg/ml) digestion of intact receptors sediment as 2.6 S species on 5–20% sucrose gradients in the presence or absence of pyridoxal phosphate. Mero-glucocoritcoid receptors prepared by exogenous proteinases are hydrophobic and show no affinity for DEAE Bio-Gel A. Treating either trypsin-generated or chymotrypsin-generated mero-receptors with pyridoxal phosphate rapidly converts the proteins (60 and 35%, respectively) into forms that bind to DEAE Bio-Gel A. Induction of DEAE binding is specific to pyridoxal phosphate, for treating mero-receptors with pyridoxal, pyridoxamine or pyridoxine phosphate is ineffective. Furthermore, DEAE binding cannot be induced by adding other pyridoxal phosphate-treated cytosols to untreated mero-receptors. High-resolution polyacrylamide gel isoelectric focussing studies indicated that treating mero-receptor generated by either proteinase with pyridoxal phosphate shifted the isoelectric points of lower pH values. The conversion of the mero-receptor to a more acidic form also occurred when the intact glucocorticoid receptor was treated with the vitamin prior to proteolysis. These studies localize at least one pyridoxal phosphate binding site on the mero-receptor domain of the rat thymocyte glucocorticoid receptor. 相似文献
130.