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1.
2.
Effects of various single-stranded-DNA-binding proteins on reactions promoted by RecA protein 总被引:4,自引:0,他引:4
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To relate the roles of Escherichia coli SSB in recombination in vivo and in vitro, we have studied the mutant proteins SSB-1 and SSB-113, the variant SSBc produced by chymotryptic cleavage, the partially homologous variant F SSB (encoded by the E. coli sex factor), and the protein encoded by gene 32 of bacteriophage T4. All of these, with the exception of SSB-1, augmented both the initial rate of homologous pairing and strand exchange promoted by RecA protein. From these and related observations, we conclude that SSB stimulates the initial formation of joint molecules by nonspecifically promoting the binding of RecA protein to single-stranded DNA; that SSB plays no role in synapsis of the RecA nucleoprotein filament with duplex DNA; that stimulation of strand exchange by SSB is similarly nonspecific; and that all members of the class of proteins represented by SSB, F SSB, and gene 32 protein may play equivalent roles in making single-stranded DNA more accessible to RecA protein. 相似文献
3.
Overexpression and DNA-binding properties of the mer-encoded regulatory protein from plasmid NR1 (Tn21). 总被引:13,自引:10,他引:3
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A Heltzel D Gambill W J Jackson P A Totis A O Summers 《Journal of bacteriology》1987,169(7):3379-3384
In plasmid NR1 the expression of genes involved in mercury resistance (Tn21) is regulated by the trans-acting product of the merR gene. An in vivo T7 RNA polymerase-promoter overexpression system was used to detect a protein of approximately 16,000 daltons encoded by the merR reading frame. Overexpressed MerR constituted about 5% of labeled proteins. An in vitro MerR-mer-op (mer-op is the mer operator and promoter region) gel electrophoresis binding assay established that the binding site for MerR was located between the putative -35 and -10 sequences of the promoter for the mer structural genes. A nonsense mutation in the carboxyl half of MerR resulted in the loss of biological function and the loss of in vitro mer-op binding properties. 相似文献
4.
Studies on the mechanism of T cell inhibition by the Pseudomonas aeruginosa phenazine pigment pyocyanine 总被引:10,自引:0,他引:10
J Nutman M Berger P A Chase D G Dearborn K M Miller R L Waller R U Sorensen 《Journal of immunology (Baltimore, Md. : 1950)》1987,138(10):3481-3487
Pseudomonas aeruginosa and its products have been shown to inhibit mitogen-induced human lymphocyte blastogenesis as measured by [3H]TdR uptake. The phenazine pigment pyocyanine has been identified as one of the inhibitors present in cellfree culture supernatants. To determine the mechanism of the inhibitory action of pyocyanine, we studied its effect on the early stages of T cell activation. Pyocyanine inhibited lymphocyte stimulation induced by specific antigens, the lectin concanavalin A and the calcium ionophore, ionomycin, suggesting that its inhibitory effect is not dependent on interference with the T cell antigen receptor complex itself. Using quin-2, we showed that pyocyanine did not interfere with the mitogen-induced increase in cytosolic-free Ca2+. We also showed that pyocyanine did not interfere with the function of calmodulin stimulated Ca2+-Mg2+ ATPase activity, indicating that the mechanism of action of pyocyanine differs from that of the structurally related phenothiazine compounds. Analysis of IL 2 production and IL 2 receptor expression clearly showed that pyocyanine inhibits the production of this essential lymphokine as well as the expression of IL 2 receptors on the T cell membrane. This inhibition is dose dependent and not due to cellular toxicity. There was parallel inhibition of growth in cell volume as well as [3H]TdR uptake. Thus, our results demonstrate that pyocyanine inhibits T cell proliferation by decreasing the production of the critical lymphokine IL 2 and by decreasing the expression of the IL 2 receptor. Local suppression of lymphocyte stimulation by phenazine pigments such as pyocyanine may interfere with cellular immune responses that may be necessary for eradication of chronic infection with P. aeruginosa. 相似文献
5.
S E Folstein G A Chase W E Wahl A M McDonnell M F Folstein 《American journal of human genetics》1987,41(2):168-179
In a Maryland survey of Huntington disease, the prevalence in blacks was unexpectedly high and equal to that in whites. Age at onset was earlier in blacks, and their clinical features, at all ages at onset, were similar to those seen in juvenile-onset Huntington disease. Blacks had more severe bradykinesia and abnormalities of eye movement and less frequent psychiatric disorder, particularly depression. 相似文献
6.
Triplet state properties of tryptophan residues in complexes of mutated Escherichia coli single-stranded DNA binding proteins with single-stranded polynucleotides.
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Complexes of point-mutated E. coli single-stranded DNA-binding protein (Eco SSB) with homopolynucleotides have been investigated by optical detection of magnetic resonance (ODMR) of the triplet state of tryptophan (Trp) residues. Investigation of the individual sublevel kinetics of the lowest triplet state of Trp residues 40 and 54 in the poly (dT) complex of Eco SSB-W88F,W135F (a mutant protein whose Trp residues at positions 88 and 135 have been substituted by Phe) shows that Trp 54 is the most affected residue upon stacking with thymine bases, confirming previous results based on SSB mutants having single Trp----Phe substitutions. (Zang, L. H., A. H. Maki, J. B. Murphy, and J. W. Chase. 1987. Biophys. J. 52:867-872). The Tx sublevel of Trp 54 shows a fourfold increase in the decay rate constant, as well as an increase in its populating rate constant by selective spin-orbit coupling. The two nonradiative sublevels show no change in lifetime, relative to unstacked Trp. For Trp 40, a weaker perturbation of Tx by thymine results in a sublevel lifetime about one-half that of normal Trp. Trp54 displays a 2[E]transition of negative polarity in the double mutant SSB complex with Poly (dT), but gives a vanishingly weak [D] - [E] signal, thus implying that the steady-state sublevel populations of Tx and Tz are nearly equal in this residue. Poly (5-BrU) induces the largest red-shift of the Eco SSB-W88F,W135F Trp phosphorescence 0,0-band of all polynucleotides investigated. Its phosphorescence decay fits well to two exponential components of 1.02 and 0.12 s, with no contribution from long-lived Trp residues. This behavior provides convincing evidence that both Trp 40 and 54 are perturbed by stacking with brominated uridine. The observed decrease in the Trp [D] values further confirms the stacking of the Trp residues with 5-BrU. Wave-length-selected ODMR experiments conducted on the [D[ + [E] transition of Eco SSB-W88F,W135F complexed with poly(5HgU) indicate the presence of multiple heavy atom-perturbed sites. Measurements made on poly (5-HgU) which each of its 4 Trp residues has been replaced in turn by Phe demonstrate that Trp 40 and 54 are the only Trp residues undergoing stacking with nucleotide bases, as previously proposed. 相似文献
7.
C. E. Vallejos C. D. Chase 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1991,81(3):413-419
Summary Backcross and F2 progenies were produced between two bean genotypes, XR-235 and Calima, which differ in seed weight by a factor of two. The small-seeded XR-235 was used as the pistillate and recurrent parent. These genotypes showed polymorphisms at nine isozyme loci and at the phaseolin locus. Seed size parameters (weight, length, width, and thickness) were determined for each BC1 and F2 individual, i.e., for seeds harvested from XR-235 after pollination with F1 and from the F1 after selfing, respectively. A combination of starch gel electrophoresis and enzyme activity staining was used to determine the genotype of each BC1 and F2 individual at the segregating loci. SDS-PAGE and Coomassie blue staining were used to determine geno-type at the phaseolin locus. Tests for independent assortment using two-way contingency and maximum likelihood tables revealed three linkage pairs: Aco-1 — 20 cM — Dia-1; Adh-1 — 2 cM — Got-2; and Est-2 — 11 cM — Pha. Statistical comparisons were made between the means of genotype classes at each segregating locus for all seed size parameters. The results from two independently obtained BC1s and the F2 consistently indicated that the Adh-1-Got-2 segment was linked to a locus that affected seed size and overcame maternal control over seed size. This locus has been designated Ssz-1. This gene exhibited additive gene action and accounted for 30–50% of the seed size difference between the parents.Florida Agricultural Experiment Station, Journal Series No. R00696 相似文献
8.
C. E. Vallejos C. D. Chase 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1991,82(3):353-357
Summary The linkage relationship of 11 bean (Phaseolus vulgaris) seed proteins (including phaseolin), 9 enzyme loci, and theP locus were analyzed in backcross and F2 progenies by use of the software package Mapmaker. The progenies were obtained by crossing the breeding line XR-235-1 and the cultivar Calima. Allelic differences for seed protein loci were detected with SDS-PAGE and those for enzyme loci with starch gel electrophoresis and activity stains. The seed coat color of Calima is a red/beige mottled pattern and that of XR-235-1 is white. Segregation at theP locus was followed by recording the phenotype of the BC1S1 and F3 seed. A linkage group comprising ca. 90 cM was detected with the following gene order:Est-2 — 11 —Pha — 8 — (Spe/Spg) — 24 — P — 9 — (Spa/Spv) — 16 —Spba — 22 —Mdh-1. In addition, another linkage group was detected: (Spd/Spf/Sph) — 5 -Spca. Therefore, the seed proteins appear to be organized in clusters in the bean genome.Florida Agricultural Experiment Station, Journal Series No. R-01131 相似文献
9.
10.
J M Braughler R L Chase J F Pregenzer 《Biochemical and biophysical research communications》1988,153(3):933-938
Peroxidation of rat brain synaptosomes was assessed by the formation of thiobarbituric acid reactive products in either 50 mM potassium phosphate buffer (pH 7.4) or pH adjusted saline. In phosphate, addition of Fe2+ resulted in a dose-related increase in lipid peroxidation. In saline, stimulation of lipid peroxidation by Fe2+ was maximal at 30 uM, and was less at concentrations of 100 uM and above. Whereas desferrioxamine caused a dose-related inhibition of iron-dependent lipid peroxidation in phosphate, it stimulated lipid peroxidation with Fe2+ by as much as 7-fold in saline. The effects of desferrioxamine depended upon the oxidation state of iron, and the concentration of desferrioxamine and lipid. The results suggest that lipid and desferrioxamine compete for available iron. The data are consistent with the hypothesis that either phosphate or desferrioxamine may stimulate iron-dependent lipid peroxidation under certain circumstances by favoring formation of Fe2+/Fe3+ ratios. 相似文献