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排序方式: 共有69条查询结果,搜索用时 15 毫秒
41.
G.B. Zavilgelsky V.Yu. Kotova I.V. Manukhov 《Mutation Research - Genetic Toxicology and Environmental Mutagenesis》2007,634(1-2):172-176
Seven different recombinant bioluminescent strains of Escherichia coli containing, respectively, the promoters katG and soxS (responsive to oxidative damage), recA (DNA damage), fabA (membrane damage), grpE, and rpoE (protein damage) and lac (constitutive expression) fused to the bacterial operon from Photorhabdus luminescens, were used to describe the mechanism of toxicity of 1,1-dimethylhydrazine (1,1-DMH) on bacteria, as well as to determine whether bacteria can sensitively detect the presence of this compound. A clear response to 1,1-DMH was observed only in E. coli carrying the katG’::lux, soxS’::lux, and recA’::lux-containing constructs. Preliminary treatment with catalase of the medium containing 1,1-DMH completely diminished the stress-response of the PkatG, PrecA, and PsoxS promoters. In the strain E. coli (pXen7), which contains a constitutive promoter, the level of cellular toxicity caused by the addition of 1,1-DMH was dramatically reduced in the presence of catalase.It is suggested that the action of 1,1-DMH on bacterial cells is determined by hydrogen peroxide, which is formed in response to reduction of the air oxygen level. 相似文献
42.
The role of chaperones Hsp70 (DnaK–DnaJ–GrpE) and Hsp100 (ClpA–ClpB–ClpX) in refolding of thermoinactivated luciferase from the marine bacterium Photobacterium fischeri and the terrestrial bacterium Photorhabdus luminescens has been studied. These luciferases are homologous, but differ greatly in the rate of thermal inactivation and the rate constant for the luminescence reaction. It was shown that refolding of thermoinactivated luciferases is completely determined by the DnaK–DnaJ–GrpE system. However these luciferases markedly differ in the rate and degree of refolding. The degree of refolding of thermolabile quick Ph. fischeri luciferase reaches 80% of the initial level over several minutes, whereas renaturation of thermostable slow Ph. luminescens luciferase proceeds substantially slower (the degree of renaturation reaches only 7-8% of the initial level over tens of minutes). The measurement of the rate of thermal inactivation of luciferases in vivo in the cells of Escherichia coli wild strain and strains containing mutations in genes clpA, clpB, clpX showed that Ph. luminescens luciferase revealed reduced thermostability in mutant strain E. coli clpA–. It was shown that this effect was not connected with DnaK-dependent refolding. In the case of thermolabile Ph. fischeri luciferase, mutation in gene clpA has no effect on the shape of the curve of thermal inactivation. These data suggest that denatured Ph. luminescens luciferase has enhanced affinity with respect to chaperone ClpA in comparison with DnaK, whereas thermolabile Ph. fischeri luciferase is characterized by enhanced affinity with respect to chaperone DnaK. Denatured luciferase bound to ClpA does not aggregate and following refolding proceeds probably spontaneously and very quickly (over 1-2 min). It is evident that the process under discussion requires ATP, since the addition of uncoupler of oxidative phosphorylation carbonyl cyanide 3-chlorophenylhydra-zone results in a sharp decrease in thermal stability of luciferase to the level typical of the enzyme in vitro. The enhanced thermosensitivity of luciferases was observed also in E. coli containing mutations in gene clpB. However, this effect, which takes place for Ph. fischeri luciferase as well as for Ph. LuminescensM luciferase, is determined by DnaK-dependent refolding and probably connected with the ability of chaperone ClpB to provide disaggregation of the proteins, resulting in their interaction with chaperones of the Hsp70 family (DnaK–DnaJ–GrpE). 相似文献
43.
A new strain of luminescent marine bacteria of the genus Aliivibrio (formerly Vibrio) was isolated from the intestines of a goby Cottida sp. (Sea of Okhotsk basin; the strain was marked as KCh1). The basic conditions of growth on laboratory media were determined
for the strain. Strain KCh1 was shown to be a psychrophilic bacterium with an optimal growth temperature of approximately
15°C. The nucleotide sequence of the 16S rRNA gene was determined and shown to be almost identical to the 16S rRNA gene sequence
of Aliivibrio logei and A. salmonicida but considerably different from that of A. fischeri. The biochemical characteristics (nitrate reduction, lysine decarboxylation, and D-galactose fermentation) of strain KCh1
matched those of A. logei and A. fischeri strains. An antibioticogram for strain KCh1 was determined. The lux operon of the strain was cloned in Escherichia coli cells and partially sequenced, the results show a high homology with the lux operon of A. salmonicida. 相似文献
44.
Rate and level of DnaKJE-dependent refolding of the thermoinactivated Aliivibrio fischeri luciferase are considerably lower in Escherichia coli ibpA and ibpB, clpA mutants than in wild type cells. The rate and level of refolding are lower in E. coli ibpB::kan than in ibpA::kan cells. The decline of refolding level in E. coli clpA::kan makes progress only with the increase of thermoinactivation time of luciferase. Plasmids with genes ibpAB do not compensate clpA mutation. It is supposed that small chaperones IpbAB and chaperone ClpA operate independently in a process of DnaKJE-dependent
refolding of proteins at the different stages. 相似文献
45.
Variation in rates of molecular evolution now appears to be widespread. The
demonstration that body size is correlated with rates of molecular
evolution suggests that physiological and ecological factors may be
involved in molecular rate variation, but large-scale comparative studies
are still lacking. Here, we use complete cytochrome b sequences from 85
species of tube-nosed seabirds (order Procellariiformes) and 5 outgroup
species of penguins (order Sphenisciformes) to test for an association
between body mass and rates of molecular evolution within the former avian
order. Cladistic analysis of the 90 sequences estimates a phylogeny largely
consistent with the traditional taxonomy of the Procellariiformes. The
Diomedeidae, Procellariidae, and Pelecanoididae are monophyletic, while the
Hydrobatidae are basal and paraphyletic. However, the two subfamilies
within the Hydrobatidae (Hydrobatinae and Oceanitinae) are monophyletic. A
likelihood ratio test detects significant deviation from clocklike
evolution in our data. Using a sign test for an association between body
mass and branch length in the seabird phylogeny, we find that larger taxa
tend to have shorter terminal branch lengths than smaller taxa. This
observation suggests that rates of mitochondrial DNA evolution are slower
for larger taxa. Rate calibrations based on the fossil record reveal
concordant body size effects. We interpret these results as evidence for a
metabolic rate effect, as the species in this order exhibit large
differences in metabolic rates, which are known to be highly correlated
with body mass in this group. Our results support previous findings of body
size effects and show that this effect can be significant even within a
single avian order. This suggests that even lineage-specific molecular
clocks may not be tenable if calibrations involve taxa with different
metabolic rates.
相似文献
46.
The structural basis of molecular adaptation 总被引:10,自引:21,他引:10
The study of molecular adaptation has long been fraught with difficulties,
not the least of which is identifying out of hundreds of amino acid
replacements those few directly responsible for major adaptations. Six
studies are used to illustrate how phylogenies, site- directed mutagenesis,
and a knowledge of protein structure combine to provide much deeper
insights into the adaptive process than has hitherto been possible. Ancient
genes can be reconstructed, and the phenotypes can be compared to modern
proteins. Out of hundreds of amino acid replacements accumulated over
billions of years those few responsible for discriminating between
alternative substrates are identified. An amino acid replacement of modest
effect at the molecular level causes a dramatic expansion in an ecological
niche. These and other topics are creating the emerging field of
"paleomolecular biochemistry."
相似文献
47.
O. E. Melkina I. I. Goryanin I. V. Manukhov A. V. Baranova V. A. Kolb M. S. Svetlov G. B. Zavilgelsky 《Biochemistry. Biokhimii?a》2014,79(1):62-68
The refolding of thermally inactivated protein by ATP-independent trigger factor (TF) and ATP-dependent DnaKJE chaperones was comparatively analyzed. Heterodimeric (αβ) bacterial luciferases of Aliivibrio fischeri, Photobacterium leiognathi, and Vibrio harveyi as well as monomeric luciferases of Vibrio harveyi and Luciola mingrelica (firefly) were used as substrates. In the presence of TF, thermally inactivated heterodimeric bacterial luciferases refold, while monomeric luciferases do not refold. These observations were made both in vivo (Escherichia coli ΔdnaKJ containing plasmids with tig gene) and in vitro (purified TF). Unlike TF, the DnaKJE chaperone system refolds both monomeric and heterodimeric luciferases with equal efficiency. 相似文献
48.
Subunit structure in the walls of sectioned microtubules was first noted by Ledbetter and Porter (6), who clearly showed that certain microtubules of plant meristematic cells have 13 wall protofilaments when seen in cross section. Earlier, protofilaments of microtubular elements had been described in negatively stained material, although exact counts of their number were difficult to obtain. In microtubular elements of axonemes, some success has been achieved in visualizing protofilaments in conventionally fixed and sectioned material (8, 10); much less success has been achieved in identifying and counting protofilaments of singlet cytoplasmic microtubules. By using glutaraldehyde-tannic acid fixation, as described by Misuhira and Futaesaku (7), Tilney et al. (12) studied microtubules from a number of sources and found that all have 13 protofilaments comprising their walls. These authors note that "...the number of subunits and their arrangement as protofilaments appear universal...". Preliminary studies of ventral nerve cord of crayfish fixed in glutaraldehyde-tannic acid indicated that axonal microtubules in this material possess only 12 protofilaments (4). On the basis of this observation, tannic acid preparations of several other neuronal and non-neuronal systems were examined. Protofilaments in microtubules from these several cell types are clearly demonstrated, and counts have been made which show that some kinds of microtubules have more or fewer protofilaments than the usual 13 and that at least one kind of microtubule has an even rather than an odd number. 相似文献
49.
Chaperone GroEL/GroES and Lon protease were shown to play a role in regulating the expression of the Vibrio fischeri lux operon cloned in Escherichia coli cells. The E. coli groE mutant carrying a plasmid with the full-length V. fischeri lux regulon showed a decreased bioluminescence. The bioluminescence intensity was high in E. coli cells with mutant lonA and the same plasmid. Bioluminescence induction curves lacked the lag period characteristic of lon + strains. Regulatory luxR of V. fischeri was cloned in pGEX-KG to produce the hybrid gene GST-luxR. The product of its expression, GST-LuxR, was isolated together with GroEL and Lon upon affinity chromatography on a column with glutathione-agarose, suggesting complexation of LuxR with these proteins. It was assumed that GroEL/GroES is involved in LuxR folding, while Lon protease degrades LuxR before its folding into an active globule or after denaturation. 相似文献
50.
Genes encoding antirestriction proteins are found in transmissble plasmids (ardABC) and bacteriophage genomes (ocr, darA). Antirestriction proteins inhibit type I restriction-modification enzymes and thus protect the unmodified plasmid or phage DNA from degradation. Antirestriction proteins belong to the family of DNA-mimicry proteins, whose spatial structure mimics the B-form of DNA. Based on an analysis of the mutant forms of ArdA and Ocr obtained by site-directed mutagenesis and the native form of ArdA that specifically inhibit type I restriction enzymes but do not affect their methylase activity, a model is proposed to describe the complex formation between an antirestriction protein and a type I restriction-modification enzyme (R2M2S): antirestriction proteins can displace a DNA strand from its binding sites in the S subunit (which contacts a specific site on DNA) and in the R subunit (which translocates the DNA strand and cleaves it). Antirestriction and antimodification activities of ArdA and Ocr as a function of ardA and ocr expression levels were studied by cloning the genes under a strictly regulated promoter. 相似文献