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71.
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
72.
Regulation of epidermin biosynthetic genes by EpiQ 总被引:14,自引:1,他引:13
73.
The benthic cyanobacterium Fischerella muscicola (Thur.) Gom. UTEX 1829 produces a secondary metabolite, fischerellin, that strongly inhibits other cyanobacteria and to a lesser extent members of the Chlorophyceae. Eubacteria are not affected. The major active compound is lipophilic and exhibits a molecular ion at m/z 408. It is heat- and acid-stable but decomposes in 1 M sodium hydroxide (80° C. 1 h). Fischerellin inhibits the photosynthetic but not the respiratory electron transport of cyanobacteria and chlorophytes. Its site of action is located in PS II. Two other species of Fischerella also produce fischerellin, indicating that the synthesis of such allelochemicals might be characteristic of the genus. 相似文献
74.
Self incompatibility (SI) in Phalaris coerulescens is gametophytically determined by two unlinked multi allelic loci (S and Z). Neither the S nor Z genes have yet been cloned. As part of a map-based cloning strategy, high-resolution maps of the S and Z regions were generated from distorted segregating populations using RFLP probes from wheat, barley, oat, and Phalaris. The S locus was delimited to 0.26 cM with two boundary markers (Xwg811 and Xpsr168) and cosegregated with Xbm2 and Xbcd762. Xbcd266 was the closest marker linked to Z (0.9 cM). A high level of colinearity in the S and Z regions was found in both self-incompatible and -compatible species. The S locus was localized to the subcentromere region of chromosome 1 and the Z locus to the long arm end of chromosome 2. Several rice BAC clones orthologous to the S and Z locus regions were identified. This opens the possibility of using the rice genome sequence data to generate more closely linked markers and identify SI candidate genes. These results add further support to the conservation of gene order in the S and Z regions of the grass genomes. 相似文献
75.
Molecular basis of intercellular adhesion in the biofilm-forming Staphylococcus epidermidis 总被引:13,自引:3,他引:10
Christine Heilmann Oliver Schweitzer Christiane Gerke Nongnuch Vanittanakom Dietrich Mack Friedrich Götz 《Molecular microbiology》1996,20(5):1083-1091
The Staphylococcus epidermidis genes icaABC are involved in the synthesis of the polysaccharide intercellular adhesin (PIA), which is located mainly on the cell surface, as shown by immunofluorescence studies with PIA-specific antiserum. PIA was shown to be a linear β-1,6-linked glucosaminoglycan composed of at least 130 2-deoxy-2-amino-D-glucopyrano-syl residues of which 80–85% are N-acetylated, the rest being non-N-acetylated and positively charged. A transposon insertion in the icaABC gene cluster (ica, intercellular adhesion) led to the loss of several traits, such as the ability to form a biofilm on a polystyrene surface, cell aggregation, and PIA production. The mutant could be complemented by transformation with the IcaABC-carrying plasmid pCN27. Transfer of pCN27 into the heterologous host Staphylococcus carnosus led to the formation of large cell aggregates, the formation of a biofilm on a glass surface, and PIA expression. The nucleotide sequence of icaABC suggests that the three genes are organized in an operon and that they are co-transcribed from the mapped ica A promoter. Ica A contains four potential transmembrane helices, indicative of a membrane location. The deduced Ica A sequence shows similarity to those of polysaccharide-polymerizing enzymes, the most pronounced being with a Rhizobium meliloti N-acetylglucosaminyltransferase involved in lipo-chitin biosynthesis (22.5% overall identity and 37.4% overall similarity). This similarity suggests that Ica A has N-acetylglucosaminyltransferase activity in the formation 相似文献
76.
Benzothiadiazole induces disease resistance in Arabidopsis by activation of the systemic acquired resistance signal transduction pathway 总被引:18,自引:6,他引:12
Kay A. Lawton Leslie Friedrich Michelle Hunt Kris Weymann Terrance Delaney Helmut Kessmann Theodor Staub John Ryals 《The Plant journal : for cell and molecular biology》1996,10(1):71-82
Benzothiadiazole (BTH) is a novel chemical activator of disease resistance in tobacco, wheat and other important agricultural plants. In this report, it is shown that BTH works by activating SAR in Arabidopsis thaliana. BTH-treated plants were resistant to infection by turnip crinkle virus, Pseudomonas syringae pv ‘tomato’ DC3000 and Peronospora parasitica. Chemical treatment induced accumulation of mRNAs from the SAR-associated genes, PR-1, PR-2 and PR-5. BTH treatment induced both PR-1 mRNA accumulation and resistance against P. parasitica in the ethylene response mutants, etr1 and ein2, and in the methyl jasmonate-insensitive mutant, jar1, suggesting that BTH action is independent of these plant hormones. BTH treatment also induced both PR-1 mRNA accumulation and P. parasitica resistance in transgenic Arabidopsis plants expressing the nahG gene, suggesting that BTH action does not require salicylic acid accumulation. However, because BTH-treatment failed to induce either PR-1 mRNA accumulation or P. parasitica resistance in the non-inducible immunity mutant, nim1, it appears that BTH activates the SAR signal transduction pathway. 相似文献
77.
Quantification of net nitrogen mineralization (NNM) in soils is indispensable in order to optimize N fertilization of crops.
Two long-term laboratory incubation methods were applied to determine rates of net nitrogen mineralization (rNNM) of soils from two sites of arable land (sandy loam soil, silty loam soil) at four temperature levels (2°C, 8°C, 14°C, 21°C).
Since variability within replicates was small, the modified 12-week incubation method of Stanford and Smith (1972) using disturbed
soils allowed to establish reliable Arrhenius functions with reasonable expenditure. The fit of the functions derived from
the 5-month incubation of 23 undisturbed soil columns (4420 cm3) was worse. This was caused by greater variability and less differentiation between temperature levels. Results of both experiments
could be described best by zero-order kinetics. Mean mineralization rates of disturbed samples were approximately twice as
high than those of undisturbed samples. The suitability of both methods for the prediction of NNM at site conditions is discussed.
Actual respiration (AR) at incubation temperatures and substrate induced respiration (SIR) were measured at the end of the
incubation of undisturbed soil columns. The results presented reveal that soil microbial communities develop in a different
manner during long-term incubation at different temperatures. This behavior offends the underlying assumption that soil microbes
remain in steady-state during incubation and that rising rates are physiological reactions to temperature enhancement. Therefore
soil microbial biomass (SMB) dynamics during the experiment has to be accounted for when rates of NNM and Arrhenius functions
are established. R Merck Section editor 相似文献
78.
79.
Characterization of tobacco plants expressing a bacterial salicylate hydroxylase gene 总被引:10,自引:0,他引:10
Leslie Friedrich Bernard Vernooij Tom Gaffney Alison Morse John Ryals 《Plant molecular biology》1995,29(5):959-968
Transgenic tobacco plants that express the bacterial nahG gene encoding salicylate hydroxylase have been shown to accumulate very little salicylic acid and to be defective in their ability to induce systemic acquired resistance (SAR). In recent experiments using transgenic NahG tobacco and Arabidopsis plants, we have also demonstrated that salicylic acid plays a central role in both disease susceptibility and genetic resistance. In this paper, we further characterize tobacco plants that express the salicylate hydroxylase enzyme. We show that tobacco mosaic virus (TMV) inoculation of NahG tobacco leaves induces the accumulation of the nahG mRNA in the pathogen infected leaves, presumably due to enhanced stabilization of the bacterial mRNA. SAR-associated genes are expressed in the TMV-infected leaves, but this is localized to the area surrounding necrotic lesions. Localized acquired resistance (LAR) is not induced in the TMV-inoculated NahG plants suggesting that LAR, like SAR, is dependent on SA accumulation. When SA is applied to nahG-expressing leave's SAR gene expression does not result. We have confirmed earlier reports that the salicylate hydroxylase enzyme has a narrow substrate specificity and we find that catechol, the breakdown product of salicylic acid, neither induces acquired resistance nor prevents the SA-dependent induction of the SAR genes. 相似文献
80.
The occurrence of -d-mannosidase II activity in insect cells was studied using pyridylaminated oligosaccharides as substrates and two-dimensional HPLC and glycosidase digestion for the analysis of products. GlcNAcMan5GlcNAc2 was converted to GlcNAcMan3GlcNAc2 by each of the three cell lines investigated (Bm-N, Sf-21, and Mb-0503). The respective activity was highest in Bm-N cells which were used for further experiments. Man5GlcNAc2 was not degraded by the Bm-N cell homogenate. Thus, this -mannosidase essentially exhibits the same substrate specificity as mammalian and plant Golgi -mannosidase II. The -mannosidase II-like activity from Bm-N cells exhibits a pH optimum of 6.0–6.5, has no requirement for divalent metal ions, and is highly sensitive to swainsonine. The 1,6-linked mannosyl residue is removed first as deduced from the elution time on reversed phase HPLC of the intermediate product. The same branch preference was found with -mannosidase II from mung bean seedlings andXenopus liver. Upon ultracentrifugation of Bm-N cell homogenate, 72% of the mannosidase acting on the GlcNAcMan5GlcNAc2 substrate was found in the microsomal pellet indicating the enzyme to be membrane-boundAbbreviations Endo H (Endo D)
endo--N-acetylglucosaminidase H (D)
- GlcNAc
N-acetylglucosamine
- M3, M5, M5Gn etc.
oligosaccharides — for an explanation see Table 1
- -PA
-pyridylamine. 相似文献