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1.
Transcriptional control, translation and function of the products of the five open reading frames of the Escherichia coli nir operon 总被引:3,自引:0,他引:3
Nerina R. Harborne Lesley Griffiths Stephen J. W. Busby Jeffrey A. Cole 《Molecular microbiology》1992,6(19):2805-2813
Five open reading frames designated nirB, nirD, nirE, nirC and cysG have been identified from the DNA sequence of the Escherichia coli nir operon. Complementation experiments established that the NirB, NirD and CysG polypeptides are essential and sufficient for NADH-dependent nitrite reductase activity (EC 1.6.6.4). A series of plasmids has been constructed in which each of the open reading frames has been fused in-phase with the beta-galactosidase gene, lacZ. Rates of beta-galactosidase synthesis during growth in different media revealed that nirB, -D, -E and -C are transcribed from the FNR-dependent promoter, p-nirB, located just upstream of the nirB gene: expression is co-ordinately repressed by oxygen and induced during anaerobic growth. Although the nirB, -D and -C open reading frames are translated into protein, no translation of nirE mRNA was detected. The cysG gene product is expressed from both p-nirB and a second, FNR-independent promoter, p-cysG, located within the nirC gene. No NADH-dependent nitrite reductase activity was detected in extracts from bacteria lacking either NirB or NirD, but a mixture of the two was as active as an extract from wild-type bacteria. Reconstitution of enzyme activity in vitro required stoichiometric quantities of NirB and NirD and was rapid and independent of the temperature during mixing. NirD remained associated with NirB during the initial stages of purification of the active enzyme, suggesting that NirD is a second structural subunit of the enzyme. 相似文献
2.
Rachael V. Gallagher Lesley Hughes Michelle R. Leishman Peter D. Wilson 《Biological invasions》2010,12(12):4049-4063
Potential interactions between climate change and exotic plant invasions may affect areas of high conservation value, such
as land set aside for the protection of endangered species or ecological communities. We investigated this issue in eastern
Australia using species distribution models for five exotic vines under climate regimes for 2020 and 2050. We examined how
projected changes in the distribution of climatically suitable habitat may coincide with the remaining remnants of an endangered
ecological community—littoral rainforests—in this region. The number of known infestations of each weed in tropical, subtropical
and temperate areas was used to assess the likelihood of further expansion into areas projected to provide suitable habitat
under future conditions. Littoral rainforest reserves were consistently predicted to provide bioclimatically suitable habitat
for the five vines examined under both current and future climate scenarios. We explore the consequences and potential strategies
for managing exotic plant invasions in these protected areas in the coming decades. 相似文献
3.
E D Bershadskaia N G Fish P P Shev'ev M A Osipov V I Ogarkov 《Zhurnal mikrobiologii, epidemiologii, i immunobiologii》1986,(9):32-35
Anabol and blastolysin preparations obtained from L. bulgaricus may contain surface structural components of the initial strain with adhesion activity; of these, one is similar in specificity to L. casei adhesin and the other, to L. plantarum adhesin. The antigenic activity of anabol and blastolysin, evaluated in the immunodiffusion test, does not correlate with their capacity for binding the receptors of susceptible bacterial cells, determined in the Lactobacillus-induced hemagglutination inhibition test. 相似文献
4.
Caroline van Haaften-Day Peter Russell Susan Carr Lesley Wright 《In vitro cellular & developmental biology. Plant》1988,24(10):965-971
Summary A cell line derived from a human ovarian carcinosarcoma was established in tissue culture and in nude mice. Two sublines,
LDF and HDF, separated by discontinuous density centrifugation were also established from the parent line JoN. The cloning
efficiency of the JoN line was 21%. Morphologic features of adenocarcinoma cells characteristic of the parent JoN cells were
retained in the sublines and clones; all lines showed the same karyotype and DNA content (pseudodiploid and pseudotetraploid).
Keratin, as demonstrated immunohistochemically, was strongly expressed in the parent line JoN and the xenograft tumor, but
not at all in the LDF sublines and only moderately in the HDF sublines. Vimentin, however, was expressed in neither the parent
line JoN nor the xenograft tumor, but was present in both sublines. Transglutaminase and plasminogen activator activity was
high in the parent line JoN. Neither, sublines nor clones showed the same high enzyme activity as the parent line. It is concluded
that this human tumor line JoN is comprised of epithelial cells, capable of multidirectional differentiation. 相似文献
5.
The binding of 3H-corticosterone and 3H-11-dehydrocorticosterone to receptors in cytosol and nucleus was examined in fetal mouse brain and placenta using Sephadex gel filtration or charcoal to separate bound and unbound steroid. In the cytosol, competitive displacement of each steroid by the other was observed. The binding was unaffected by RNase, DNase, dithiothreitol or N-ethyl maleimide but was diminished by Pronase. Nuclei were isolated by hypotonic shock using dilute MgCl2 and the steroid receptor-complexes of both steroids were obtained from the nuclear sap. Receptor-complexes of both steroids were observed in brain and placental tissues. Competitive displacement of each steroid by the other was also observed in nuclear binding. Both 11-dehydrocorticosterone and 11-deoxycorticosterone bound to a chromatin fraction as did the hormone corticosterone. Identity of the steroids was established by using chromatography and co-crystallization techniques. This work raises the possibility that in the fetal mouse, 11-dehydrocorticosterone, previously considered biologically inactive and an abundant metabolite in fetal mouse tissues, may in fact play a more positive role in regulation. 相似文献
6.
Michaelis-Menten kinetics for exoglucanase, endoglucanase and β-glucosidase activities from two different strains of Aspergillus fumigatus were compared in the absence and the presence of ammonium ions. Inhibitory effects, evident in only one strain, were quantified, suggesting non-competitive inhibition for endoglucanase and β-glucosidase, but competitive inhibition of exocellulase. Possible reasons are discussed. 相似文献
7.
8.
9.
L I Kulinich N G Fish O P Mazitova S A Dratvin M O Birger 《Journal of hygiene, epidemiology, microbiology, and immunology》1987,31(3):287-292
A collection of 26 Enterobacteriaceae reference strains provided by Reference Centres in Moscow (USSR) and Copenhagen (Denmark) as well as a collection of 660 freshly isolated cultures of Gram-negative bacteria of different origin were investigated using SIB indicator systems manufactured at the Gorky Institute of Epidemiology and Microbiology (USSR) and API-20E, Rapid-20E and API-10S kits (API, France) with the aim of species determination. In analyzing freshly isolated cultures, API-20E, API-10S and SIB-B kits proved to be of approximately equal efficiency, whereas the Rapid-20E system enabled species identification in no more than 78% of the tested cultures. In a model biotyping of 284 E. coli cultures of different origin, SIB-B and API-20E kits in combination with the Analytical Profile Index enabled sufficiently rapid and standard identification of Enterobacteriaceae biovars. 相似文献
10.
Properties of DNase I digestion of the deoxyoligonucleotide: 5''d(ATCGTACGAT)2(3''). 总被引:1,自引:1,他引:0 下载免费PDF全文
Deoxyribonuclease I digestion of the deoxyoligodecamer 5'd(ATCGTACGAT)2(3') has been examined in detail to study the kinetic and structural properties of this enzyme substrate system in solution. In addition, these studies have defined, in general, those DNase I conditions to be used in future drug-DNA footprinting experiments. Special attention has been taken of those properties of DNase I that are critical for quantitation of ligand binding to small DNA fragments, and that aid in designing oligomers to be used in footprinting experiments. Enzyme activity was observed at all phosphodiester bonds in the decamer studied with varying affinity, except for the first four bonds at the 5' end of the oligomer. The DNA substrate concentration is always in excess, in order to achieve conditions of no more than one DNase I cleavage per DNA molecule. Reactions were controlled so that 65% or more of the initial amount of decamer substrate remained after DNase I digestion. It was observed that the rate of enzyme reactivity decreases with digestion time and is sensitive to the experimental conditions. 相似文献