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Intestinal synthesis of 24-keto-1,25-dihydroxyvitamin D3. A metabolite formed in vivo with high affinity for the vitamin D cytosolic receptor 总被引:1,自引:0,他引:1
J L Napoli B C Pramanik P M Royal T A Reinhardt R L Horst 《The Journal of biological chemistry》1983,258(15):9100-9107
24-Keto-1,25-dihydroxyvitamin D3 has been identified as an intestinal metabolite of 1,25-dihydroxyvitamin D3 by ultraviolet absorbance, mass spectroscopy, and chemical reactivity. The metabolite was produced from 1,25-dihydroxyvitamin D3 and 1,24R,25-trihydroxyvitamin D3 in rat intestinal mucosa homogenates. 24-Keto-1,25-dihydroxyvitamin D3 is present in vivo in the plasma and small intestinal mucosa of rats fed a stock diet, receiving no exogenous 1,25-dihydroxyvitamin D3, and in the plasma and small intestinal mucosa of rats dosed chronically with 1,25-dihydroxyvitamin D3. 24-Keto-1,25-dihydroxyvitamin D3 has affinity equivalent to 1,24R,25-trihydroxyvitamin D3 for the 3.7 S cytosolic receptor specific for 1,25-dihydroxyvitamin D3 in the intestine and thymus. In cytosolic preparations contaminated with the 5 S vitamin D-binding protein, both metabolites are about 7-fold less potent than 1,25-dihydroxyvitamin D3. In contrast, in cytosolic preparations largely free of the 5 S binding protein, both metabolites are equipotent with the parent compound. No evidence was obtained supporting a substantial presence of 23-keto-1,25-dihydroxyvitamin D3 in vivo; nor was the latter compound generated in detectable amounts from 1,25-dihydroxyvitamin D3 by intestinal homogenates. Thus, C-24 oxidation is a significant pathway of intestinal 1,25-dihydroxyvitamin D3 metabolism that produces metabolites with high affinity for the cytosolic receptor which mediates vitamin D action. 相似文献
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W Quinkler M Maasberg S Bernotat-Danielowski N Lüthe H S Sharma W Schaper 《European journal of biochemistry》1989,181(1):67-73
Fresh bovine, porcine and canine hearts were homogenized and mitogens for mesoderm-derived cells were purified in three different steps. Extraction by two different ammonium sulfate precipitations was followed by cation-exchange chromatography and by heparin-Sepharose affinity chromatography. A heparin-Sepharose fraction from heart (eluted at 1.1 M NaCl) increased mitotic activity in serum-deprived cultures of porcine aortic endothelial and smooth muscle cells, and in human fibroblasts. This mitogenic activity is potentiated by heparin and inhibited by gamma-interferon. The heart mitogenic fraction showed one double peak on HPLC at A215 and one polypeptide band on SDS/PAGE. These peaks and bands were identical to those obtained from bovine brain. The heart acidic fibroblast growth factor (aFGF) showed a positive signal in Western blots using antibodies raised against brain aFGF. Gas-phase amino acid sequencing established that the mitogens were identical to aFGF and the N-terminally truncated aFGF. Extraction in the presence of a protease inhibitor (pepstatin A) produced a higher-molecular mass form of aFGF with a blocked amino terminus. Another mitogen, eluted at 1.6 M NaCl from heparin-Sepharose, reacted with polyclonal antiserum against human recombinant basic fibroblast growth factor (bFGF) and showed a 66% (12 from 18 amino acids determined by gas-phase sequencing) similarity with bFGF. This polypeptide increased the mitotic activity of the same cell lines but was more potent than aFGF. 相似文献
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Organization of the ribosomal ribonucleic acid genes in various wild-type strains and wild-collected strains of Neurospora 总被引:6,自引:0,他引:6
Peter J. Russell Sheryl Wagner Karin D. Rodland Rhonda L. Feinbaum Jennifer P. Russell Marion S. Bret-Harte Stephen J. Free Robert L. Metzenberg 《Molecular & general genetics : MGG》1984,196(2):275-282
Summary The organization of the ribosomal DNA (rDNA) repcat unit in the standard wild-type strain of Neurospora crassa, 74-OR23-1A, and in 30 other wild-type strains and wild-collected strains of N. crassa, N. tetrasperma, N. sitophila, N. intermedia, and N. discreta isolated from nature, was investigated by restriction enzyme digestion of genomic DNA, and probing of the Southern-blotted DNA fragments with specific cloned pieces of the rDNA unit from 74-OR23-1A. The size of the rDNA unit in 74-OR23-1A was shown to be 9.20 kilobase pairs (kb) from blotting data, and the average for all strains was 9.11+0.21 kb; standard error=0.038; coefficient of variation (C.V.)=2.34%. These data indicate that the rDNA repeat unit size has been highly conserved among the Neurospora strains investigated. However, while all strains have a conserved HindIII site near the 5 end of the 25 S rDNA coding sequence, a polymorphism in the number and/or position of HindIII sites in the nontranscribed spacer region was found between strains. The 74-OR23-1A strain has two HindIII sites in the spacer, while others have from 0 to at least 3. This restriction site polymorphism is strain-specific and not species-specific. It was confirmed for some strains by restriction analysis of clones containing most of the rDNA repeat unit. The current restriction map of the 74-OR23-1A rDNA repeat unit is presented. 相似文献
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Conformational studies on substance P. C-terminal pentapeptide pGlu-Phe-Phe-Gly-Leu-Met NH2 总被引:1,自引:0,他引:1
The conformational behavior of the active C-terminal pentapeptide of substance P(SP), pGlu-Phe-Phe-Gly-Leu-Met NH2 [pGlu-SP(7–11)] was investigated using empirical energy calculations. A sequential approach was used to display the specific contribution of each residue to induce stable conformations of the whole pentapeptide. The most stable conformations include the αR helix and some partially helical structures; some conformations with glycyl residue in a C7eq and C7ax configurations (γ and turns) are also favoured. Helical conformations provide a good accessibility of side-chains which play an important role in interacting with the receptor. Fully extended structures and β turns are not specially stable. Such helical stable structures would favour a “lock and key” model of binding. 相似文献