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991.
992.
993.
Polymorphic restriction sites of type II collagen gene: their location and frequencies in the Finnish population 总被引:3,自引:0,他引:3
Restriction fragment length polymorphism (RFLP) of the cartilage-specific type II collagen gene has been studied in the Finnish population. Two high-frequency alleles, also reported in other populations, were detected. The HindIII allele had a frequency of 0.33, and that detected with PvuII a frequency of 0.46. Both of these frequencies resembled the ones reported for other populations. Also one BamHI allele, not earlier reported, was found at a low frequency. Two other previously reported polymorphisms for BamHI and EcoRI were not detected in the Finnish population. The RFLPs showed a fair agreement with the Hardy-Weinberg equilibrium. A linkage disequilibrium was found between PvuII and HindIII markers. The alpha 1(II) collagen gene seems to be more conserved in populations of various origins than the alpha 2(I) collagen gene. These polymorphic collagen markers would be useful in linkage studies of various inherited cartilage disorders. 相似文献
994.
The distribution of the phenotypes of alpha-1-antitrypsin (Pi) was investigated in a Swiss population sample of 1,148 unrelated individuals using isoelectric focusing with a immobilized pH gradient. A short focusing period of only 2 h using high-voltage is an additional asset of this modified method. All common as well as the rarer phenotypes were reliably detected. However, detection of Pi M4 required a narrower pH range as chosen for routine work. The allele frequencies found were: PiM1:0.7121; PiM2:0.1381; PiM3:0.0976; PiS:0.0383; PiZ:0.0113; PiVar(I, N, V.Vdon):0.0026. 相似文献
995.
In a Portuguese family, a null allele was found in the Pi system. An apparent 'exclusion' of the mother was found to be due to the presence of null alleles in mother and child. A transferrin (Tf) null allele was found in a case of disputed paternity. The mother and putative father were heterozygous for Tf null alleles and the child was homozygous (TfQ0) and presented hypotransferrinemia. 相似文献
996.
A highly sensitive and simple method to enhance detection of glycoproteins resolved by either one- or two-dimensional polyacrylamide gel electrophoresis is described. The method is a modification of the procedure described by D. Fargeaud et al. (D. Fargeaud, J. C. Benoit, F. Kato, and G. Chappuis (1984) Arch. Virol. 80, 69-82) that uses concanavalin A conjugated with fluorescein isothyocyanate to detect the carbohydrate moiety of glycoproteins. Briefly, the electrophoresed gel is exposed to the fluorescent lectin, thoroughly washed, and sequentially transferred to 50% methanol in deionized water and to absolute methanol. The result is an abrupt dehydration of the gel which turns evenly white and stiff. At least a twofold enhancement of fluorescence is obtained as detected by exposing the treated gel to an appropriate uv source. The sensitivity of the procedure allows us to detect purified immunoglobulin molecules by their carbohydrate content in the range of 0.2 microgram of total protein. The specificity of the detection is demonstrated by a comparison with the corresponding polypeptide profile obtained by silver nitrate staining of the gel. 相似文献
997.
Effect of amino acid substitutions and deletions on the thermal stability, the pH stability and unfolding by urea of bovine calbindin D9k 总被引:3,自引:0,他引:3
B Wendt T Hofmann S R Martin P Bayley P Brodin T Grundstr?m E Thulin S Linse S Forsén 《European journal of biochemistry》1988,175(3):439-445
The influence of amino acid substitutions and deletions on the stability of bovine calbindin D9k, the smallest protein known with a pair of EF-hand calcium-binding sites, has been studied using circular dichroism and ultraviolet absorption spectroscopy. The five modifications are confined to one of the two Ca2+ -binding sites. The Ca2+-loaded forms of the wild-type and mutant calbindins are too stable to be significantly denatured by heating at 90 degrees C or by adding 8 M urea. For the Ca2+-free (apo) forms thermal unfolding appears to be only half complete at 90 degrees C, while denaturation is complete in 7-8 M urea. Four of the mutant proteins show reduced resistance towards unfolding by urea, but one of the modified proteins (Glu-17----Gln) shows an increased stability, presumably because of a reduced electrostatic repulsion in the native state. According to X-ray crystallographic data the OH group of the single tyrosine of calbindin (Tyr-13) is hydrogen-bonded to the carboxyl group of Glu-35, thus linking the two alpha helices flanking the N-terminal Ca2+ site. The pK of ionization of the Tyr-13 hydroxyl group was over 13 for calcium forms of the wild-type protein, between 12.3 and 12.8 for the calcium form of three mutants and between 11.5 and 11.7 for the apoproteins. Significant differences in pH stability between wild type and mutants were observed in the calcium forms, but were not apparent in the apo forms. 相似文献
998.
5'-Methylbenzimidazolyl-cobamides are the corrinoids from some sulfate-reducing and sulfur-metabolizing bacteria 总被引:3,自引:0,他引:3
The sulfate-reducing bacteria Desulfobacterium autotrophicum, Desulfobulbus propionicus and Archaeoglobus fulgidus (VC-16) and the sulfur-metabolizing archaebacteria Desulfurolobus ambivalens and Thermoplasma acidophilum were found to contain considerable amounts of corrinoids, that were isolated and crystallized in their Co beta-cyano form. In three other sulfur-metabolizing archaebacteria, Thermoproteus neutrophilus, Pyrodictium occultum and Staphylothermus marinus significant amounts of corrinoids were not detected under the isolation methods used. The samples from the three sulfate-reducers were identified with Co alpha-[alpha-(5'-methylbenzimidazolyl)]-Co beta-cyanocobamide. This corrinoid was also obtained from a 5-methylbenzimidazole-supplemented Propionibacterium fermentation and was structurally characterized by ultraviolet/visible, CD, fast-atom-bombardment MS, 1H-and 13C-NMR spectroscopy. Also the major corrinoid from T. acidophilum was (tentatively) analyzed as a 5'-methylbenzimidazolyl-cobamide, whereas the main corrinoid from D. ambivalens was indicated to be vitamin B12 (a 5',6'-dimethylbenzimidazolyl-cobamide). The 5'-methylbenzimidazolylcobamides are found here as the common corrins of some sulfate-reducing and sulfur-metabolizing bacteria. The structural diversity due to the differing nucleotide bases of the corrins examined here and in methanogenic and acetogenic bacteria appears not to correlate to the biological function(s) of the corrins, but rather to be determined by biosynthetic properties of these organisms under natural growth conditions. 相似文献
999.
When calf aortic tissue, preincubated under organ culture conditions in the presence of [35S]sulfate, was submitted to a sequential collagenase and elastase digestion and guanidinium chloride extraction, the bulk of proteoheparan sulfate was obtained in the elastase fraction. Ion-exchange chromatography on DEAE-cellulose of the elastase digest under dissociative conditions yielded a proteoglycan fraction that contained heparan sulfate as the sole glycosaminoglycan. The proteoheparan sulfate fraction was resolved into a high-molecular-mass (P-HS 1) and a low-molecular-mass (P-HS 2) fraction by gel filtration on Sephacryl S-400. P-HS 1 has a Mr of 175,000 and possesses four heparan sulfate side-chains (Mr 32,000) covalently bound to the protein core via a galactose- and xylose-containing polysaccharide-protein binding region. The protein core (Mr 38,000), which was obtained after deglycosylation of PG-HS 1 with trifluormethane sulfonic acid, contained in addition a few N-glycosidically linked oligosaccharide units representing a complex type with terminal neuraminic acid residues. P-HS 2 is a single-chain peptidoheparan sulfate of Mr of 38,000 containing one heparan sulfate chain (Mr 32,000) linked to a polypeptide (Mr 6000). The ratio of specific radioactivities of P-HS 1 and P-HS 2 was 1:0.66. 相似文献
1000.
Rapid-scan stopped-flow studies of the flavoenzyme mercuric reductase during catalytic turnover 总被引:1,自引:0,他引:1
Time-resolved absorption spectra of the FAD-containing enzyme mercuric reductase were recorded during the catalytic reaction at 25 degrees C, pH 7.3. With an excess of NADPH over Hg2+ there was a rapid (k = 43 s-1) initial formation of a spectral species similar to that previously assigned to an NADPH complex of two-electron-reduced enzyme, EH2-NADPH. This spectrum persisted during the quasisteady-state phase of the reaction suggesting that EH2-NADPH is a true catalytic intermediate and that the rate of catalysis is limited by the oxidation of EH2-NADPH by Hg2+. Also with an excess of Hg2+ over NADPH a spectrum similar to that of EH2-NADPH was rapidly formed. As the NADPH was exhausted, the spectrum of oxidized enzyme, E, did not reappear but rather a spectrum similar to that previously assigned to an NADP+ complex of two-electron-reduced enzyme, EH2-NADP+. These results suggest that EH2-HADP+ cannot rapidly reduce the Hg2+ substrate. However, eventually all reducing equivalents from NADPH added to oxidized, activated enzyme are utilized for the reduction of Hg2+. A mechanism model is proposed that does not involve the free, oxidized enzyme in the catalytic cycle. 相似文献