共查询到20条相似文献,搜索用时 46 毫秒
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Luminal brush border and contraluminal basal-lateral segments of the plasma membrane from the same kidney cortex were prepared. The brush border membrane preparation was enriched in trehalase and γ-glutamyltranspeptidase, whereas the basal-lateral membrane preparation was enriched in (Na+ + K+)-ATPase. However, the specific activity of (Na+ + K+)-ATPase in brush border membranes also increased relative to that in the crude plasma membrane fraction, suggesting that (Na+ + K+)-ATPase may be an intrinsic constituent of the renal brush border membrane in addition to being prevalent in the basal-lateral membrane. Adenylate cyclase had the same distribution pattern as (Na+ + K+)-ATPase, i.e. higher specific activity in basal-lateral membranes and present in brush border membranes. Adenylate cyclase in both membrane preparations was stimulated by parathyroid hormone, calcitonin, epinephrine, prostaglandins and 5′-guanylylimidodiphosphate. When the agonists were used in combination enhancements were additive. In contrast to the distribution of adenylate cyclase, guanylate cyclase was found in the cytosol and in basal-lateral membranes with a maximal specific activity (NaN3 plus Triton X-100) 10-fold that in brush border membranes. ATP enhanced guanylate cyclase activity only in basal-lateral membranes. It is proposed that guanylate cyclase, in addition to (Na+ + K+)-ATPase, be used as an enzyme “marker” for the renal basal-lateral membrane. 相似文献
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The effect of alcohols on the spectral properties of riboflavin derivatives in non-polar solvent was studied by various spectroscopic methods in order to support the view point that alcohol may directly interact with the isoalloxazine moiety of FAD and enhance the catalytic activity of D-amino acid oxidase (DAAO). The most likely association complex between alcohol and riboflavin is 1 : 1 stoichiometric complex through the 3-N imino and the 2-C carbonyl groups of the isoalloxazine ring and the hydroxyl group of alcohols. It appears that methanol has a larger association constant than any other alcohols, and the association constant decreases with the increase in carbon number and with the steric requirement of the alkyl group of alcohols. 相似文献
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Paradoxical stimulation by 1-methyl-3-isobutylxanthine of rat liver cyclic AMP phosphodiesterase activity 总被引:1,自引:0,他引:1
DNA newly synthesized in UV irradiated Escherichia coli B/r Hcr+ was 2 min pulse-labeled at various periods, then denatured and analysed by sucrose gradient centrifugation either in neutral or in alkaline conditions. Data indicate that in DNA of damaged cells alkali-labile sites are produced. In cells saturated with inducible proteins production of alkali-labile sites disappears in ~1 h. In the absence of inducible proteins production of alkali-labile sites continues. 相似文献
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John M. Rosenberg Nadrian C. Seeman Roberta O. Day Alexander Rich 《Journal of molecular biology》1976,104(1):145-167
The crystal structure of sodium guanylyl-3′,5′-cytidine (GpC) nonahydrate has been determined by X-ray diffraction procedures and refined to an R value of 0.054. GpC crystallizes with four molecules per monoclinic unit cell, space group C2, with cell dimensions: . Two molecules of GpC related by the 2-fold axis of the crystal form a small segment of right-handed, anti-parallel double-helical RNA in the crystal. Guanine is paired to cytosine through three hydrogen bonds of lengths 2.91, 2.95 and 2.86 Å. The bases along each strand are heavily stacked at a distance of about 3.4 Å. The fragments form skewed flattened rods within the lattice by the inter-molecular stacking of guanines with each other and the stacking of cytosine with the guanosine Ol′atom. The sodium cations are bound only to the ionized phosphate groups in this structure and exhibit face-sharing octahedral co-ordination. The sodium cations serve to bridge the rods of GpC fragments and organize them into sheets within the crystal. There are 18 water molecules per double-helical fragment which are all part of the first co-ordination shell of nitrogen, oxygen or sodium atoms. 相似文献
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Ordered transcription of RNA tumor virus genomes. 总被引:43,自引:0,他引:43
W A Haseltine D G Kleid A Panet E Rothenberg D Baltimore 《Journal of molecular biology》1976,106(1):109-131
The crystal structure of sodium adenylyl-3′,5′-uridine (ApU) hexahydrate has been determined by X-ray diffraction procedures and refined to an R factor of 0.057. ApU crystallizes with two molecules per asymmetric unit in a monoclinic unit cell, space group P21, with cell dimensions: . The two independent molecules of ApU form a small segment of right-handed antiparallel double-helical RNA in the crystal, with Watson-Crick base-pairing between adenine and uracil. This is the first time that this Watson-Crick base-pair has been seen unambiguously at atomic resolution and it is also the first time that a nucleic acid fragment with double-helical symmetry has been seen at atomic resolution. The distance between the C1′ atoma of the adenine-uracil base-pair is slightly shorter than the analogous distance seen in guanine-cytosine base-pairs. The bases in each strand are heavily stacked. One sodium cation binds to the phosphates, as expected; however, the other sodium cation binds on the dyad axis in the minor groove of the double helix. It is co-ordinated directly to the two uracil carbonyl groups which protrude into the minor groove and is shielded from the nearest phosphates by a shell of water. This binding appears to be sequence-specific for ApU. One of the adenines also forms a pair of hydrogen bonds to a nearby ribose, utilizing N6 and N7. The 12 water molecules per double-helical fragment are all part of the first co-ordination shell. The ions and the symmetry of the double-helical fragment are the major organizing elements of the solvent region. 相似文献
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Rat liver cytosol binds 3H-cAMP and 3H-DBcAMP . Fractionation of bound radioactivity by DEAE-Sephadex chromatography shows that 3H-cAMP is associated with a different cytosolic protein than is 3H-DBcAMP. The pI's of the cAMP-protein and the 3H-DBcAMP-protein complexes are 6.7 and 3.9, respectively. Competition studies between 3H-cAMP and its structural analogues have shown the following order of effectiveness in competing for binding sites in rat liver cytosol: cAMP > N6-MBcAMP > O2′-MBcAMP. No inhibition of 3H-cAMP binding was observed with 5′-AMP, adenosine, cGMP or DBcAMP. binding experiments with rat serum has shown that only 3H-DBcAMP binds to any significant extent. 相似文献
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A.A.leslie Gunatilaka Sarath R. Sirimanne Subramaniam Sotheeswaran H.T.Badra Sriyani 《Phytochemistry》1982,21(3):805-806
From the bud exudates of Gardenia cramerii and G. fosbergii, two species endemic to Sri Lanka, a new flavonoid with an unusual B-ring oxidation pattern, 5,5′-dihydroxy-6,7,2′,3′-tetramethoxyflavone, was characterized. Two other rare flavonoids, 5,3′,5′-trihydroxy-3,6,7,4′-tetramethoxyflavone and 5-hydroxy-6,7,3′,4′,5′-pentamethoxyflavone were also isolated from both Gardenia species. 相似文献
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Guanylate cyclase of plasma membrane of isolated rat fat cells was activated 7 to 11 fold by oleic acid, linoleic acid, linolenic acid or arachidonic acid. The activation of the enzyme by linoleic acid or oleic acid was influenced by the concentration of enzyme protein and that of the fatty acid. At 158 μg/ml of enzyme protein, 0.6 mM linoleic acid produced maximal activation of 12 fold which was partially reversed by washing. Particulate guanylate cyclase of cerebral cortex and liver was also activated by linoleic acid. 相似文献
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Leovigildo Quijano José S. Calderón Federico Gómez G Edgar Escobar Tirso Rios 《Phytochemistry》1985,24(5):1085-1088
Two new highly oxygenated flavones, were isolated from aerial parts of Ageratum houstonianum. Their structures were established as 3′-hydroxy-5,6,7,8,2′,4′,5′-heptamethoxyflavone and 5,3′-dihydroxy-6,7,8,2′,4′,5′-hexamethoxyflavone on the basis of spectral data and chemical degradation. The structure of the latter compound was confirmed by X-ray analysis. 相似文献
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Mamoru Sano 《Biochimica et Biophysica Acta (BBA)/General Subjects》1976,428(2):525-531
The subcellular localizations of guanylate cyclase and 3′,5′-cyclic nucleotide phophodiesterase in sea urchin sperm were examined. Both the specific and total activities of these two enzymes were much higher in sperm flagella (tails) than in the heads. In addition to the observation that guanylate cyclase in the flagella was particulate-bound and solubilized by Triton X-100, more than 980% of the cyclase activity in the flagella was found in the plasma membrane fraction, whereas the activity of cyclic nucleotide phosphodiesterase was observed in both the axonemal and plasma membrane fractions. The observations indicated that the cyclase in the flagella appeared to be associated with the plasma membrane. Cyclic nucleotide phosphodiesterase in the plasma membrane fraction as well as the axonemal fraction hydrolyzed both cyclic GMP and cyclic AMP; however, the rates of hydrolysis for cyclic GMP were obviously higher than those for cyclic AMP. The enzymic properties of guanylate cyclase and cyclic nucelotide phosphodiesterase in sperm flagella were also briefly described. 相似文献
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The use of thin acrylamide gels for DNA sequencing 总被引:477,自引:0,他引:477
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Chloroform extraction of Eupatorium leucolepis gave the new flavones 3′-hydroxy-5,6,7,8,4′,5′-hexamethoxyflavone, 4′-hydroxy-5,6,7,8,3′,5 相似文献
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S R Wagle R Stermann K Decker 《Biochemical and biophysical research communications》1976,71(2):622-628
Effect of galactosamine on glycogenolysis was studied in isolated hepatocytes. It was found that addition of galactosamine strongly inhibited glycogenolysis in normal hepatocytes. Galactosamine-inhibited glycogenolysis was not stimulated by epinephrine or glucagon. This inhibition was specific as no such inhibition was observed with galactose, 2-deoxy-glucose or glucosamine. The glucagon-stimulated cyclic AMP formation in galactosamine-treated hepatocytes was the same as in normal cells; Glc-1-P and Glc-6-P did not accumulate nor was lactate formation enhanced. The glucose production by hepatocytes from regenerating liver was only slightly inhibited by galactosamine and glucagon addition stimulated glycogenolysis in the presence of the amino sugar. 相似文献
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From the leaves of Myrica gale 2′,4′-dihydroxy-6′-methoxy-3′,5′-dimethylchalcone has been isolated. The fruits yielded 2′-hydroxy-4′,6′-dimethoxy-3′-methyldihydrochalcone. The constitutions were deduced from spectroscopic data and confirmed by synthesis. 相似文献