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31.
Sylvia Hagemann Wolfgang J. Miller Wilhelm Pinsker 《Molecular & general genetics : MGG》1994,244(2):168-175
The genome of Drosophila bifasciata harbours two distinct subfamilies of P-homologous sequences, designated M-type and O-type elements based on similarities to P element sequences from other species. Both subfamilies have some general features in common: they are of similar length (M-type: 2935 bp, O-type: 2986 bp), are flanked by direct repeats of 8 by (the presumptive target sequence), contain terminal inverted repeats, and have a coding region consisting of four exons. The splice sites are at homologous positions and the exons have the coding capacity for proteins of 753 amino acids (M-type) and 757 amino acids (O-type). It seems likely that both types of element represent functional transposons. The nucleotide divergence of the two P element subfamilies is high (31%). The main structural difference is observed in the terminal inverted repeats. Whereas the termini of M-type elements consist of 31 by inverted repeats, the inverted repeats of the O-type elements are interrupted by non-complementary stretches of DNA, 12 by at the 5 end and 14 by at the 3 end. This peculiarity is shared by all members of the O-type subfamily. Comparison with other P element sequences indicates incongruities between the phylogenies of the species and the P transposons. M-type and O-type elements apparently have no common origin in the D. bifasciata lineage. The M-type sequence seems to be most closely related to the P element from Scaptomyza pallida and thus could be considered as a more recent invader of the D. bifasciata gene pool. The origin of the O-type elements cannot be unequivocally deduced from the present data. The sequence comparison also provides new insights into conserved domains with possible implications for the function of P transposons. 相似文献
32.
The gene encoding the extracellular neutral metalloprotease ShpI from Staphylococcus hyicus subsp. hyicus was cloned. DNA sequencing revealed an ORF of 1317 nucleotides encoding a 438 amino acid protein with Mr of 49698. When the cloned gene was expressed in Staphylococcus carnosus, a 42 kDa protease was found in the culture medium. The protease was purified from both S. carnosus (pCAshp1) and S. hyicus subsp. hyicus. The N-terminal amino acid sequences of the two proteases revealed that ShpI is organized as a pre-pro-enzyme with a proposed 26 amino acid signal peptide, a 75 amino acid hydrophilic pro-region, and a 337 amino acid extracellular mature form with a calculated Mr of 38394. The N-termini showed microheterogeneity in both host strains. ShpI had a maximum proteolytic activity at 55°C and pH 7.4–8.5. The protease, which had a low substrate specificity, could be inhibited by metal- and zinc-specific inhibitors, such as EDTA and 1,10-phenanthroline. Insensitivity to phosphoramidon separates ShpI from the thermolysin-like family. The conserved Zn2+ binding motif, the only homology to other proteases, and the reactivation of the apoenzyme by Zn2+, indicated that Zn2+ is the catalytic ion. Ca2+ very probably acts as a stabilizer. We also demonstrated the presence of a second extracellular protease in S. hyicus subsp. hyicus. 相似文献
33.
Identification and Cloning of Genes Involved in Specific Desulfurization of Dibenzothiophene by Rhodococcus sp. Strain IGTS8 总被引:14,自引:3,他引:11 下载免费PDF全文
The gram-positive bacterium Rhodococcus sp. strain IGTS8 is able to remove sulfur from certain aromatic compounds without breaking carbon-carbon bonds. In particular, sulfur is removed from dibenzothiophene (DBT) to give the final product, 2-hydroxybiphenyl. A genomic library of IGTS8 was constructed in the cosmid vector pLAFR5, but no desulfurization phenotype was imparted to Escherichia coli. Therefore, IGTS8 was mutagenized, and a new strain (UV1) was selected that had lost the ability to desulfurize DBT. The genomic library was transferred into UV1, and several colonies that had regained the desulfurization phenotype were isolated, though free plasmid could not be isolated. Instead, vector DNA had integrated into either the chromosome or a large resident plasmid. DNA on either side of the inserted vector sequences was cloned and used to probe the original genomic library in E. coli. This procedure identified individual cosmid clones that, when electroporated into strain UV1, restored desulfurization. When the origin of replication from a Rhodococcus plasmid was inserted, the efficiency with which these clones transformed UV1 increased 20- to 50-fold and they could be retrieved as free plasmids. Restriction mapping and subcloning indicated that the desulfurization genes reside on a 4.0-kb DNA fragment. Finally, the phenotype was transferred to Rhodococcus fascians D188-5, a species normally incapable of desulfurizing DBT. The mutant strain, UV1, and R. fascians produced 2-hydroxybiphenyl from DBT when they contained appropriate clones, indicating that the genes for the entire pathway have been isolated. 相似文献
34.
A psychrotrophic toxin-producing strain of Aeromonas hydrophila grew well in a range of food slurries (scallop, prawn, fish, chicken liver paté, liverwurst, chicken luncheon slice and commercial baby food preparations) held at refrigeration temperatures. In most foods, excluding the baby food preparations, exotoxins were produced at levels comparable with production in bacteriological broth without apparent food spoilage (all but prawn and fish). Addition of ultra-heat treated (UHT) milk to toxin-containing broth culture supernatants markedly decreased or removed haemolytic and cytotoxic activities, explaining low levels of toxins found in milk in a previous study. Baby food preparations did not inactivate exotoxins under similar conditions suggesting production of toxins rather than their inactivation was inhibited in these foods. 相似文献
35.
Seasonal dynamics of the association between sweet potato and vesicular-arbuscular mycorrhizal fungi 总被引:2,自引:0,他引:2
To better understand the behavior of selected vesicular-arbuscular mycorrhizal (VAM) isolates in the field, we documented the growth of roots, root hairs, and VAM colonization of inoculated and noninoculated sweet potato plants (Ipomea batatas (L.) Lam. cv White Star) over a growing season. We also determined the seasonal dynamics of P and Zn uptake, and shoot and storage-root growth. Shoot cuttings were inoculated with an isolate of either Glomus etunicatum Becker and Gerdemann or Acaulospora rugosa Mortan, or were not inoculated, and were harvested 2, 4, 8, 13, 20, and 27 weeks after planting (WAP). At each harvest, roots were sampled at 0 to 30, 30 to 60, and 60 to 90 cm depths and at 0, 23, 83, and 116 cm from the base of the shoot. At the end of the study, the roots of three non-inoculated plants were sampled by soil horizon. Inoculation had no affect on shoot growth or total shoot uptake of P and Zn; shoot dry mass and P and Z content increased rapidly up to 20 WAP, while shoot length continued to increase through 27 WAP. Shoot-P concentration of plants inoculated with A. rugosa at 2 and 8 WAP were higher than the noninoculated plants, while shoot-Zn concentration was not affected by inoculation. Storage-root yields of inoculated plants were higher than yields for noninoculated plants. Root length density, and percentage of root length with root hairs and VAM colonization were highest and most dynamic near the base of the plant. Percentage of root length colonization by VAM fungi was highest in the E2 horizon, intermediate in the Bh horizon, and lowest in the Ap horizon. Percentage of root length with root hairs had the opposite pattern. Intensive measurements of root characteristics close to the base of the plant, and shoot P-content and concentration during the period of rapid yield production, provided the most useful data for evaluating the activity of effective isolates.Published as Florida Agricultural Experimental Station Journal Series No. R-02576 相似文献
36.
Isolation and characteristics of a wheatbran-degrading Butyrivibrio from human faeces 总被引:1,自引:0,他引:1
Corinne J. Rumney Sylvia H. Duncan C. Henderson C.S. Stewart 《Letters in applied microbiology》1995,20(4):232-236
Screening over 100 isolates from human faeces for cellulolytic activity led to the isolation of a weakly cellulolytic anaerobic, curved, motile bacterium which produced H2 , lactate and butyrate from wheatbran. The mol% of G + C in the DNA was 39–42. These properties, together with the Gram-positive cell wall ultrastructure and SDS-PAGE profile, are consistent with the genus Butyrivibrio. The isolate is believed to be the most active wheatbran-degrading bacterium so far described. 相似文献
37.
Expression of insulin-like growth factor II (IGF-II) and histological changes in the thymus and spleen of transgenic mice overexpressing IGF-II 总被引:2,自引:0,他引:2
Leo T. M. Van der Ven Paul J. M. Roholl Maria G. Reijnen-Gresnigt Ruud J. Bloemen Sylvia C. van Buul-Offers 《Histochemistry and cell biology》1997,107(3):193-203
Previously, transgenic mice were constructed overexpressing human insulin-like growth factor II (IGF-II) under control of
the H2kb promoter. The IGF-II transgene was highly expressed in thymus and spleen, and these organs showed an increase in weight. In
the current study we have analyzed the sites of IGF-II mRNA expression, the distribution of IGF-II, IGF-I, and both IGF receptors,
and histomorphometrical changes in thymus and spleen. With in situ mRNA hybridization, expression of the IGF-II transgene
is found with high intensity in the thymic medulla and in the white pulp/marginal zone of the spleen, whereas there were scattered
positive cells in the thymic cortex and in the splenic red pulp. Hybridization was restricted to non-lymphocytic cells. Immunohistochemistry
revealed intense IGF-II peptide staining with the same distribution as IGF-II mRNA. There was additional intense IGF-II staining
of all elements in the splenic red pulp (including trabeculae) and diffuse, low level staining in the thymic cortex. These
findings were not observed in control mice. In the thymic medulla, most IGF-II producing cells co-labelled with keratin, whereas
a minor population also stained for the monocyte/macrophage marker MOMA-2. In the spleen, co-labelling of IGF-II producing
cells was found with MOMA-1 (marginal zone), or with the dendritic cell marker NLDC-145 (red pulp). IGF-I and both IGF receptors
were found in these organs in nearly all cell types, with a similar pattern in transgenic mice and in control animals. Histomorphometric
analysis revealed a marked increase of thymus cortex size and an increased trabecular size in the spleen. This suggests that
IGF-II overproduction induces local effects (auto/paracrine) in the thymic cortex, but not in the thymic medulla. Trabecular
growth in the spleen most likely is a distant effect (paracrine or endocrine) of IGF-II overproduction.
Accepted: 5 September 1996 相似文献
38.
Evidence for Linkage of Bipolar Disorder to Chromosome 18 with a Parent-of-Origin Effect 总被引:16,自引:8,他引:8 下载免费PDF全文
O. Colin Stine Jianfeng Xu Rebecca Koskela Francis J. McMahon Michele Gschwend Carl Friddle Chris D. Clark Melvin G. McInnis Sylvia G. Simpson Theresa S. Breschel Eva Vishio Kelly Riskin Harriet Feilotter Eugene Chen Susan Shen Susan Folstein Deborah A. Meyers David Botstein Thomas G. Marr J. Raymond DePaulo 《American journal of human genetics》1995,57(6):1384-1394
A susceptibility gene on chromosome 18 and a parent-of-origin effect have been suggested for bipolar affective disorder (BPAD). We have studied 28 nuclear families selected for apparent unilineal transmission of the BPAD phenotype, by using 31 polymorphic markers spanning chromosome 18. Evidence for linkage was tested with affected-sib-pair and LOD score methods under two definitions of the affected phenotype. The affected-sib-pair analyses indicated excess allele sharing for markers on 18p within the region reported previously. The greatest sharing was at D18S37: 64% in bipolar and recurrent unipolar (RUP) sib pairs (P = .0006). In addition, excess sharing of the paternally, but not maternally, transmitted alleles was observed at three markers on 18q: at D18S41, 51 bipolar and RUP sib pairs were concordant for paternally transmitted alleles, and 21 pairs were discordant (P = .0004). The evidence for linkage to loci on both 18p and 18q was strongest in the 11 paternal pedigrees, i.e., those in which the father or one of the father's sibs is affected. In these pedigrees, the greatest allele sharing (81%; P = .00002) and the highest LOD score (3.51; θ = 0.0) were observed at D18S41. Our results provide further support for linkage of BPAD to chromosome 18 and the first molecular evidence for a parent-of-origin effect operating in this disorder. The number of loci involved, and their precise location, require further study. 相似文献
39.
A series of mutations in mice was tested for splenic NK-cell activity against YAC-1 target cells. Mutations at six loci that reduce NK-cell activity in the homozygous state were identified, including beige (bg), hairless (hr), motheaten (me), obese (ob), steel (Sl) and, to a lesser extent, dominant spotting (W). Motheaten mice displayed the most profound NK-cell deficiency, with NK-cell activity virtually absent. Two mutations, nude (nu) and lymphoproliferation (Ipr), produced elevated NK-cell-mediated lysis. The double homozygous recessivenu/nu bg/bg nude-beige mouse was viable and NK-cell-deficient, with activity slightly higher than that of +/?bg/bg beige littermate controls. Pigmentation mutants related to beige, including pale ears (ep), pearl (pe), and ruby eyes (ru 2J ) did not dramatically influence NK-cell levels. Unlike the obese gene, other mutations leading to obesity, diabetes (db) and yellow (Asuy), did not impair NK-cell function. The possible site of gene action of these mutants in the NK-cell pathway is discussed. 相似文献
40.
G G Choudhury V L Sylvia A Y Sakaguchi 《The Journal of biological chemistry》1991,266(34):23147-23151
Receptor tyrosine kinases couple to multiple intracellular effector molecules that are crucial for normal cell growth and transformation. Stimulation of membrane phospholipid hydrolysis by receptor tyrosine kinases is one such pathway for generating intracellular second messengers that may be important for mitogenesis. Certain receptor tyrosine kinases tyrosine phosphorylate a phosphoinositide-specific phospholipase C that hydrolyses the membrane phospholipid phosphatidylinositol 4,5-bisphosphate. In contrast, the glycoprotein receptor for colony stimulating factor 1, a transmembrane tyrosine kinase, does not utilize this pathway, but rather stimulates the hydrolysis of phosphatidylcholine. Here we show that eluates of antiphosphotyrosine affinity purified lysates of colony-stimulating factor 1-stimulated cells contain elevated levels of phosphatidylcholine-specific phospholipase C activity. The affinity-purified activity is sensitive to tyrosine-specific T-cell phosphatase, and is detected in the membrane fraction of stimulated cells. Recovery of phospholipase C activity in the antiphosphotyrosine protein fraction is reduced by pertussis toxin pretreatment of cells. The phosphatidylcholine phospholipase C activity in isolated membranes of colony-stimulating factor 1-treated cells was also reduced by pertussis toxin treatment and stimulated by guanosine 5'-3-O-(thio)triphosphate. These results indicate that colony stimulating factor 1 receptor-mediated stimulation of phosphatidylcholine-specific phospholipase C requires tyrosine phosphorylation, and might be affected by a G-protein coupled pathway. 相似文献