共查询到20条相似文献,搜索用时 0 毫秒
1.
Ching-Nan Lin Wan-Jr Syu Wei-Sheng W Sun Jenn-Wei Chen Tai-Hung Chen Ming-Jaw Don Shao-Hung Wang 《Journal of biomedical science》2010,17(1):84
Plumbagin is found in many herbal plants and inhibits the growth of various bacteria. Escherichia coli strains are relatively resistant to this drug. The mechanism of resistance is not clear. Previous findings showed that plumbagin
treatment triggered up-regulation of many genes in E. coli including ahpC, mdaB, nfnB, nfo, sodA, yggX and ygfZ. By analyzing minimal inhibition concentration and inhibition zones of plumbagin in various gene-disruption mutants, ygfZ and sodA were found critical for the bacteria to resist plumbagin toxicity. We also found that the roles of YgfZ and SodA in detoxifying
plumbagin are independent of each other. This is because of the fact that ectopically expressed SodA reduced the superoxide
stress but not restore the resistance of bacteria when encountering plumbagin at the absence of ygfZ. On the other hand, an ectopically expressed YgfZ was unable to complement and failed to rescue the plumbagin resistance
when sodA was perturbed. Furthermore, mutagenesis analysis showed that residue Cys228 within YgfZ fingerprint region was critical for
the resistance of E. coli to plumbagin. By solvent extraction and HPLC analysis to follow the fate of the chemical, it was found that plumbagin vanished
apparently from the culture of YgfZ-expressing E. coli. A less toxic form, methylated plumbagin, which may represent one of the YgfZ-dependent metabolites, was found in the culture
supernatant of the wild type E. coli but not in the ΔygfZ mutant. Our results showed that the presence of ygfZ is not only critical for the E coli resistance to plumbagin but also facilitates the plumbagin degradation. 相似文献
2.
Kurt Frunzke Bernd Heiss Ortwin Meyer Walter G. Zumft 《FEMS microbiology letters》1993,113(2):241-245
Abstract Respiratory nitrate reductase from the denitrifying bacterium Pseudomonas stutzeri is an iron-sulfur enzyme containing the molybdenum cofactor. Hydrolysis of native nitrate reductase with aqueous sulfuric acid revealed 0.92 mol of 5'-GMP per mol of enzyme. The pterin present in the molybdenum cofactor was liberated from the protein and reacted with iodoacetamide. The resulting di(carboxamidomethyl) (cam) derivative was purified on a C18 -cartridge and analyzed for its structural elements. Treatment of the cam derivative with nucleotide pyrophosphatase and subsequent HPLC analysis revealed the formation of di(cam)molybdopterin and 5'-GMP at a 1:1 molar ratio and with a yield of 79% with respect to the molybdenum content of the enzyme. Treatment of the cam derivative with nucleotide pyrophosphatase and alkaline phosphatase led to the liberation of 0.51 mol dephosphodi(cam)molybdopterin and of 0.59 mol guanosine per mol of enzyme, which is equal to a molar ratio of 1:2.2. The results indicate, that the organic moiety of the molybdenum cofactor of nitrate reductase from P. stutzeri is molybdopterin guanine dinucleotide of which one mol is contained per mol of nitrate reductase. 相似文献
3.
Simon C. Drew Karrera Y. Djoko Lianyi Zhang Melissa Koay John F. Boas John R. Pilbrow Zhiguang Xiao Kevin J. Barnham Anthony G. Wedd 《Journal of biological inorganic chemistry》2008,13(6):899-907
Continuous-wave and pulsed electron paramagnetic resonance have been applied to the study of the Cu(II) site of the copper-resistance protein PcoC from Escherichia coli and certain variant forms. Electron spin echo envelope modulation (ESEEM) experiments confirm the presence of two histidine ligands, His1 and His92, at the Cu(II) site of wild-type PcoC, consistent with the available X-ray crystallographic data for the homolog CopC (67% sequence identity) from Pseudomonas syringae pv. tomato. The variants H1F and H92F each lack one of the histidine residues close to the Cu(II) site. The ESEEM data suggest that the surviving histidine residue remains as a ligand. The nA variant features an extra alanine residue at the N terminus, which demotes the His1 ligand to position 2. At least one of the two histidine residues is bound at the Cu(II) site in this form. Simulation of the (14)N superhyperfine structure in the continuous-wave spectra confirms the presence of at least three nitrogen-based ligands at the Cu(II) sites of the wild-type, H92F and nA forms, while the H1F variant has two nitrogen ligands. The spectra of wild-type form can be fitted adequately with a 3N or a 4N model. The former is consistent with the crystal structure of the CopC homolog, where His1 acts as a bidentate ligand. The latter raises the possibility of an additional unidentified nitrogen ligand. The markedly different spectra of the H1F and nA forms compared with the wild-type and H92F proteins further highlight the integral role of the N-terminal histidine residue in the high-affinity Cu(II) site of PcoC. 相似文献
4.
Lena Jansson Jonas Ångström Michael Lebens Susann Teneberg 《Glycoconjugate journal》2010,27(1):171-179
A novel carbohydrate binding site recognizing blood group A and B determinants in a hybrid of cholera toxin and Escherichia coli heat-labile enterotoxin B-subunits (termed LCTBK) has previously been described, and also the native heat-labile enterotoxin bind to some extent to blood group A/B terminated
glycoconjugates. The blood group antigen binding site is located at the interface of the B-subunits. Interestingly, the same
area of the B-subunits has been proposed to be involved in binding of the heat-labile enterotoxin to lipopolysaccharides on
the bacterial cell surface. Binding of the toxin to lipopolysaccharides does not affect the GM1 binding capacity. The present
study aimed at characterizing the relationship between the blood group A/B antigen binding site and the lipopolysaccharide
binding site. However, no binding of the B-subunits to E. coli lipopolysaccharides in microtiter wells or on thin-layer chromatograms was obtained. Incubation with lipopolysaccharides
did not affect the binding of the B-subunits of heat-labile enterotoxin of human isolates to blood group A-carrying glycosphingolipids,
indicating that the blood group antigen site is not involved in LPS binding. However, the saccharide competition experiments
showed that GM1 binding reduced the affinity for blood group A determinants and vice versa, suggesting that a concurrent occupancy of the two binding sites does not occur. The latter finding is related to a connection
between the blood group antigen binding site and the GM1 binding site through residues interacting with both ligands. 相似文献
5.
6.
Jorge Hernandez Valeria Prado Daniel Torres Jonas Waldenström Paul D. Haemig Björn Olsen 《Polar Biology》2007,30(10):1227-1229
Rectal swabs were collected from Antarctic fur seal pups Arctocephalus gazella at Cape Shirreff, South Shetland Islands, and analyzed for the presence of anthropogenic pathogens. Two of the 33 pups tested
positive for enteropathogenic Escherichia coli (EPEC). These samples are the first records of EPEC in Antarctic wildlife and suggest that more needs to be done to protect
the Antarctic fauna from exotic anthropogenic pathogens. 相似文献
7.
Shuyu Wu Eirini Chouliara Lars Bogø Jensen Anders Dalsgaard 《Acta veterinaria Scandinavica》2008,50(1):38
Background
Screening and enumeration of antimicrobial resistant Escherichia coli directly from samples is needed to identify emerging resistant clones and obtain quantitative data for risk assessment. Aim of this study was to evaluate the performance of 3M™ Petrifilm™ Select E. coli Count Plate (SEC plate) supplemented with antimicrobials to discriminate antimicrobial-resistant and non-resistant E. coli. 相似文献8.
Background
The mRNA translation initiation region (TIR) comprises the initiator codon, Shine-Dalgarno (SD) sequence and translational enhancers. Probably the most abundant class of enhancers contains A/U-rich sequences. We have tested the influence of SD sequence length and the presence of enhancers on the efficiency of translation initiation. 相似文献9.
10.
Renu Nandakumar Christophe Espirito Santo Nandakumar Madayiputhiya Gregor Grass 《Biometals》2011,24(3):429-444
Metallic copper surfaces have strong antimicrobial properties and kill bacteria, such as Escherichia coli, within minutes in a process called contact killing. These bacteria are exposed to acute copper stress under dry conditions
which is different from chronic copper stress in growing liquid cultures. Currently, the physiological changes of E. coli during the acute contact killing process are largely unknown. Here, a label-free, quantitative proteomic approach was employed
to identify the differential proteome profiles of E. coli cells after sub-lethal and lethal exposure to dry metallic copper. Of the 509 proteins identified, 110 proteins were differentially
expressed after sub-lethal exposure, whereas 136 proteins had significant differences in their abundance levels after lethal
exposure to copper compared to unexposed cells. A total of 210 proteins were identified only in copper-responsive proteomes.
Copper surface stress coincided with increased abundance of proteins involved in secondary metabolite biosynthesis, transport
and catabolism, including efflux proteins and multidrug resistance proteins. Proteins involved in translation, ribosomal structure
and biogenesis functions were down-regulated after contact to metallic copper. The set of changes invoked by copper surface-exposure
was diverse without a clear connection to copper ion stress but was different from that caused by exposure to stainless steel.
Oxidative posttranslational modifications of proteins were observed in cells exposed to copper but also from stainless steel
surfaces. However, proteins from copper stressed cells exhibited a higher degree of oxidative proline and threonine modifications. 相似文献
11.
Hang Yu Xin Meng Francis Worlanyo Kwami Aflakpui Lixin Luo 《Annals of microbiology》2016,66(2):727-736
12.
A putative β-glucosidase gene from the genome of Bacillus halodurans C-125 was expressed in E. coli under the regulation of T7lac promoter. On induction with isopropyl-β-D-1-thiogalactopyranoside, the enzyme expressed at ∼40% of the cell protein producing
238 mg/liter culture. With increase in culture cell density to A
600 12 in auto-inducing M9NG medium, β-glucosidase production increased 3-fold. Approximately 70% of the expressed enzyme was
in a soluble form, while the rest was in an insoluble fraction of the cell lysate. The soluble and active form of the expressed
enzyme was purified by ammonium sulfate precipitation followed by ion-exchange chromatography to a purity >98%. The mass of
the enzyme as determined by MALDI-TOF mass spectrometry was 51,601 Da, which is nearly the same as the calculated value. Phylogenetic
analysis of the β-glucosidase of B. halodurans was found to cluster with members of the genus Bacillus. Temperature and pH optima of the enzyme were found to be 45°C and 8.0, respectively, under the assay conditions. K
m and k
cat against p-nitrophenyl-β-D-glucopyranoside were 4 mM and 0.75 sec−1, respectively. To our knowledge, this is the first report of high-level expression and characterization of a β-glucosidase
from B. halodurans. 相似文献
13.
A nonenzymatic glycation of the recombinant leghemoglobin expressed in Escherichia coli cells was demonstrated for the first time. This process involved the heme pocket and gave low-spin leghemoglobin species.
A correlation between the degree of E. coli protein glycation and synthesis of poly-β-hydroxybutyric acid was found, suggesting that the accumulation of reserve carbon
sources and nonenzymatic glycation could be alternative processes. 相似文献
14.
The use of lignocellulose as a source of sugars for bioproducts requires the development of biocatalysts that maximize product
yields by fermenting mixtures of hexose and pentose sugars to completion. In this study, we implicate mgsA encoding methylglyoxal synthase (and methylglyoxal) in the modulation of sugar metabolism. Deletion of this gene (strain
LY168) resulted in the co-metabolism of glucose and xylose, and accelerated the metabolism of a 5-sugar mixture (mannose,
glucose, arabinose, xylose and galactose) to ethanol. 相似文献
15.
Shaofang Liu Yingjie Chen Yandu Lu Huaxin Chen Fuchao Li Song Qin 《Photosynthesis research》2010,105(2):135-142
Allophycocyanin (APC), a cyanobacterial photosynthetic phycobiliprotein, functions in energy transfer as a light-harvesting
protein. One of the prominent spectroscopic characteristics of APC is a strong red-shift in the absorption and emission maxima
when monomers are assembled into a trimer. Previously, holo-APC α and β subunits (holo-ApcA and ApcB) were successfully synthesized
in Escherichia coli. In this study, both holo-subunits from Synechocystis sp. PCC 6803 were co-expressed in E. coli, and found to self-assemble into trimers. The recombinant APC trimer was purified by metal affinity and size-exclusion chromatography,
and had a native structure identical to native APC, as determined by characteristic spectroscopic measurements, fluorescence
quantum yield, tryptic digestion analysis, and molecular weight measurements. Combined with results from a study in which
only the monomer was formed, our results indicate that bilin synthesis and the subsequent attachment to apo-subunits are important
for the successful assembly of APC trimers. This is the first study to report on the assembly of recombinant ApcA and ApcB
into a trimer with native structure. Our study provides a promising method for producing better fluorescent tags, as well
as a method to facilitate the genetic analysis of APC trimer assembly and biological function. 相似文献
16.
The question of whether discontinuous DNA replication operates only for the lagging strand or for both strands in E. coli remains unresolved. In this study, the participation of priA, B, C and rep genes in discontinuous DNA replication was examined by analyzing the size distribution of nascent DNA synthesized in wild-type,
lig-7 and polA4113 genetic backgrounds. Inactivation of priA, but not priB, priC or rep, resulted in a significant increase of high molecular weight (HMW) DNA in the short pulse-labeled DNA in the wild-type lig
+
polA
+
strains. Inactivation of priA also produced a significant increase of HMW DNA in the nascent DNA synthesized in lig-7 and polA4113 strains. These results indicate that PriA is involved in the discontinuous synthesis of nascent DNA. 相似文献
17.
R. Jayaraman 《Journal of genetics》2009,88(3):379-391
Mutators (also called hypermutators) are mutants which show higher than normal spontaneous mutation frequencies, ranging from
10–20 fold to 100–1000 fold higher, or sometimes even more, than wild-type cells. Being a mutator is advantageous to the organism
when adapting to environmental changes or stressful situations, such as moving from one habitat to another, one host to another,
exposure to antibiotics etc. However, this advantage is only a short-term benefit. In the long run, hypermutability leads
to a fitness disadvantage due to accumulation of deleterious mutations or antagonistic pleiotropy or both. Contrary to intuitive
expectations, hypermutability is commonly encountered in natural bacterial populations, especially among clinical isolates.
It is believed to be involved in the emergence of antibiotic resistance and a hindrance to the treatment of infectious diseases.
Here, I review the state of knowledge on the common mechanisms of hypermutability such as errors/defects in DNA replication,
proof reading, mismatch repair, oxidative DNA damage, mistranslation etc., as well as phenomena associated with these processes,
using Escherichia coli as a paradigmatic organism. 相似文献
18.
The purpose of this work was to characterize the cellular and proteomic responses of Escherichia coli JK-17 exposed to the rose flower extract (Rosa hybrida). The bacterial isolate was enriched and isolated from contaminated food. 16S rRNA sequence analyses revealed that the strain
was 99% similar to the E. coli species cluster; therefore, this strain was designated E. coli JK-17. The rose flower extract showed a dose-dependent antibacterial effect on E. coli JK-17. Treatment of E. coli JK-17 with 50 and 100 mg/mL of the rose flower extract completely inhibited growth within 12 and 6 h of incubation. The stress
shock proteins (SSPs) were induced with different concentrations of rose flower extract. The proteins were identified as 70-kDa
DnaK and 60-kDa GroEL by SDS-PAGE and Western blot using anti-DnaK and anti-GroEL monoclonal antibodies. The levels of SSPs
induced by the rose flower extract increased when the exposure time to the rose flower extract was increased. SDS-PAGE with
silver staining revealed that the amount of lipopolysaccharide (LPS) in E. coli JK-17 increased or decreased with different concentrations and exposure times of the rose flower extract. To identify proteins
induced by the rose flower extract, 2-dimensional electrophoresis (2-DE) was applied to soluble protein fractions of E. coli JK-17 cultures. In the pH range of 4 ∼ 7, more than 250 spots were detected on the silver stained gels. Notably, 15 protein
spots were increased or decreased after treatment with the rose flower extract. Twelve up-regulated proteins were identified
as chaperones (DnaK and GroEL) and porin proteins (PhoE, RfaI, RfaG, MdoH, and WzzE) by MALDITOF mass spectrometry, and three
down-regulated proteins were identified, including proteins involved in energy and DNA metabolism (SdhA and GyrB), and amino
acid biosynthesis (GltK). Using scanning electron microscopic analysis, some cells were shown to adopt irregular rod shapes
and wrinkled surfaces after treatment with the rose flower extract. These results provide clues for better understanding the
mechanism of rose flower extract-induced stress and cytotoxicity in E. coli JK-17. 相似文献
19.
20.
Resistance to butanol is a key factor affecting microbial ability to produce economically profitable amounts of butanol. In
this study, an Escherichia coli strain capable of growth in the presence of 1.5% butanol was isolated. The mutant MG1655 ButR was characterized by increased
resistance to ethanol, isopropanol, and bivalent ions but exhibited supersensitivity to osmotic shock. Compared to the wild
type strain, the butanol-tolerant mutant was more sensitive to antibiotics inhibiting protein synthesis but was more resistant
to membrane-penetrating antibiotics, such as surfactin. Increased content of unsaturated fatty acids was found in the membranes
of butanol-tolerant mutants. It was revealed that overexpression of the genes encoding cold-shock proteins decreased butanol
tolerance of both mutant and the wild-type strain. It was concluded that butanol tolerance was associated with multiple rearrangements
of the cell genetic system, rather than with single mutations. 相似文献