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1.
Hydroquinone is a benzene-derived metabolite. To clarify whether the reactive oxygen species (ROS) are involved in hydroquinone-induced cytotoxicity, we constructed transformants of Escherichia coli (E. coli) strains that express mammalian catalase gene derived from catalase mutant mice (Cs(b), Cs(c)) and the wild-type (Cs(a)) using a catalase-deficient E. coli UM255 as a recipient. Specific catalase activities of these tester strains were in order of Cs(a) > Cs(c) > Cs(b) > UM255, and their susceptibility to hydrogen peroxide (H2O2) showed UM255 > Cs(b) > Cs(c) > Cs(a). We found that hydroquinone exposure reduced the survival of catalase-deficient E. coli mutants in a dose-dependent manner significantly, especially in the strains with lower catalase activities. Hydroquinone toxicity was also confirmed using zone of inhibition test, in which UM255 was the most susceptible, showing the largest zone of growth inhibition, followed by Cs(b), Cs(c) and Cs(a). Furthermore, we found that hydroquinone-induced cell damage was inhibited by the pretreatment of catalase, ascorbic acid, dimethyl sulfoxide (DMSO), and ethylenediaminetetraacetic acid (EDTA), and augmented by superoxide dismutase (both CuZnSOD and MnSOD). The present results suggest that H2O2 is probably involved in hydroquinone-induced cytotoxicity in catalase-deficient E. coli mutants and catalase plays an important role in protection of the cells against hydroquinone toxicity. 相似文献
2.
M. G. Klotz Y. C. Kim J. Katsuwon A. J. Anderson 《Applied microbiology and biotechnology》1995,43(4):656-666
The phytopathogenic, gram-negative bacterium Pseudomonas syringae pv. syringae 61 contains three isozymes of catalase (EC 1.11.1.6), which have been proposed to play a role in the bacterium's responses to various environmental stresses. To study the role of individual isozymes, the gene coding for the catalytic subunit of one catalase isozyme was cloned from a cosmid library hosted in Escherichia coli DH5 by using a designed catalase-specific DNA probe for the screening. One out of four clones with a catalase-positive genotype was subcloned and a pUC19-based 2.7 × 103-base (2.7-kb) insert subclone, pMK3E5, was used to transform catalase-deficient E. coli strain UM255 (HPI–, HPII–). The transformants contained a single isozyme of catalase that had electrophoretic and enzymic properties similar to catalase isozyme CatF from P. syringae pv. syringae 61. Analysis of the sequenced 2.7-kb insert DNA revealed six putative open-reading frames (ORF). The 1542-base-pair DNA sequence of ORF2, called catF, encodes a peptide of 513 amino acid residues with a calculated molecular mass of 66.6 kDa. The amino acid sequence deduced from catF had homology to the primary structure of true catalases from mammals, plants, yeasts and bacteria. The activity of the recombinant catalase was inhibited by 3-amino-1,2,4-triazole and azide and stimulated by chloramphenicol. The N terminus contained a signal sequence of 26 amino acids necessary for secretion into the periplasm, a so-far unique property of Pseudomonas catalases.Paper no. 4552 of the Utah Agricultural Experiment station 相似文献
3.
Abdelhakim Sellal Rima Belattar Abdelouahab Bouzidi 《International journal of phytoremediation》2019,21(5):456-460
AbstractIn this study, roots, stems and leaves of the worldwide distributed macrophyte Phragmites australis (common reed) were tested as potential removal and biomonitors of trace elements contamination in sediment. In particular, the concentrations (100, 200, and 500?mg/kg) of the following elements were analyzed: Zn, Cu, Pb, and Fe. Results showed that the amount of concentrations in plant tissues is significantly (p?≤?0.01) dependent on the kind of organ and element. Trace element concentrations decreased according to the pattern of Fea (Rootsa > Stemsb > Leavesb) > Znb (Roota > Leavesb > Stemsc) > Cuc (Rootsa > Leavesb > Stemsc) > Pbc (Rootsa > Stemsb > Leavesc), as well as the roots acted as the main centers of bioaccumulation for all elements studied, and stems as the transit organs for translocation from roots to leaves. The major mechanisms employed by the plant were probably phytostabilization on the basis of the calculated Biological Concentration Factor (BCF – metal concentration ratio of plant root to soil); and Translocation Factor (TF – metal concentration ratio of plants roots to above ground part). Finally, due to the low scavenger effect of the radical DPPH, we excluded the hypothesis of the use of antioxidant mechanism in the tolerance of metals. 相似文献
4.
Hepatic microsomes of acatalasemic Csb mice subjected to heat inactivation displayed decreased catalatic activity but NADPH dependent microsomal ethanol oxidation (MEOS) remained active and unaffected. Even without heat inactivation, in the Csb strain, the NADPH dependent metabolism of ethanol was much more active than the H2O2 mediated one whereas microsomes of Csa control mice displayed equal rates of H2O2 and NADPH dependent ethanol oxidation. Addition of catalase to liver microsomes in vitro abolished this difference whereas the catalase inhibitor azide established in the Csa mice a pattern similar to that of the Csb, namely a much more active NADPH dependent than a H2O2 mediated ethanol oxidation. The selective persistence in the Csb mice of NADPH dependent ethanol oxidation contrasting with the reduction in the H2O2 mediated metabolism of ethanol supports the existence of a microsomal ethanol oxidizing system independent of catalase. 相似文献
5.
When liver slices of Csa and Csb mice were incubated , they had similar catalase activities and equal rates of ethanol metabolism. While incubated liver homogenates and microsomes from Csa mice oxidized ethanol and retained catalase activity, preparations from Csb mice did not oxidize ethanol and lost all catalase activity. Addition of beef liver catalase restored ethanol oxidation by Csb microsomes. The oxidations of aniline and aminopyrine proceeded at the same rate in Csa and Csb microsomes and were inhibited by ethanol. It is evident that (a) the microsomal drug-metabolizing pathway is not involved in ethanol oxidation, and (b) the postulation of a unique microsomal ethanol-oxidizing system (“MEOS”) that is independent of microsomal catalase is unwarranted. 相似文献
6.
Lorentzen MS Moe E Jouve HM Willassen NP 《Extremophiles : life under extreme conditions》2006,10(5):427-440
The gene encoding catalase from the psychrophilic marine bacterium Vibrio salmonicida LFI1238 was identified, cloned and expressed in the catalase-deficient Escherichia coli UM2. Recombinant catalase from V. salmonicida (VSC) was purified to apparent homogeneity as a tetramer with a molecular mass of 235 kDa. VSC contained 67% heme b and 25% protoporphyrin IX. VSC was able to bind NADPH, react with cyanide and form compounds I and II as other monofunctional small subunit heme catalases. Amino acid sequence alignment of VSC and catalase from the mesophilic Proteus mirabilis (PMC) revealed 71% identity. As for cold adapted enzymes in general, VSC possessed a lower temperature optimum and higher catalytic efficiency (k
cat/K
m) compared to PMC. VSC have higher affinity for hydrogen peroxide (apparent K
m) at all temperatures. For VSC the turnover rate (k
cat) is slightly lower while the catalytic efficiency is slightly higher compared to PMC over the temperature range measured, except at 4°C. Moreover, the catalytic efficiency of VSC and PMC is almost temperature independent, except at 4°C where PMC has a twofold lower efficiency compared to VSC. This may indicate that VSC has evolved to maintain a high efficiency at low temperatures. 相似文献
7.
1. E. coli, strain K-12, and B. megatherium 899, irradiated in strict but still undefined physiological conditions with certain heavy doses of ultraviolet light, are efficiently restored by catalase, which acts on or fixes itself upon the bacteria in a few minutes. This restoration (C. R.), different from photorestoration, is aided by a little visible light. 2. At 37° the restorability lasts for about 2 hours after UV irradiation; the restored cells begin to divide at the same time as the normal survivors. 3. C. R. is not produced after x-irradiation. 4. B. megatherium Mox and E. coli, strain B/r show little C. R.; E. coli strain B shows none. None of these three strains is lysogenic, whereas the two preceding catalase-restorable strains are. 5. Phage production in the system "K-12 infected with T2 phage" is restored by catalase after UV irradiation, whereas phage production in the system "infected B" is not. 6. With K-12, catalase does not prevent the growth of phage and the lysis induced by UV irradiation (Lwoff's phenomenon). 7. Hypotheses are discussed concerning: (a) the chemical nature of this action of catalase; (b) a possible relation between C. R. and lysogenicity of the sensitive bacteria; (c) the consequences of such chemical restorations on the general problem of cell radiosensitivity. 相似文献
8.
Aims: To model the effect of water activity (aw) and concentration of undissociated lactic acid (HLac) on the time to growth (TTG) and the growth/no growth boundary of acid‐adapted generic Escherichia coli, used as model organisms for Shiga toxin‐producing E. coli (STEC). Methods and Results: For each of two E. coli strains, the TTG in brain heart infusion broth at 27°C was estimated at 30 combinations of aw (range 0·945–0·995) and concentration of HLac (range 0–6·9 mol m?3) by using an automated turbidity reader. Survival analysis was used to develop a model predicting the TTG and the growth/no growth boundary. Conclusions: The present model can be used to predict the TTG and to indicate the growth/no growth boundary of acid‐adapted E. coli strains as a function of aw and concentration of HLac. Significance and Impact of the Study: Fermented food products have been implicated as sources of STEC in several outbreaks. The study results are relevant for modelling of growth of STEC in fermented food and can be used in microbiological risk assessments or in the design and validation of food‐production processes. 相似文献
9.
NMR Spectroscopy has been established as a major tool for identification and quantification of metabolites in a living system. Since the metabolomics era began, one‐dimensional NMR spectroscopy has been intensively employed due to its simplicity and quickness. However, it has suffered from an inevitable overlap of signals, thus leading to inaccuracy in identification and quantification of metabolites. Two‐dimensional (2D) NMR has emerged as a viable alternative because it can offer higher accuracy in a reasonable amount of time. We employed 1H,13C‐HSQC to profile metabolites of six different laboratory E. coli strains. We identified 18 metabolites and observed clustering of six strains according to their metabolites. We compared the metabolites among the strains, and found that a) the strains specialized for protein production were segregated; b) XL1‐Blue separated itself from others by accumulating amino acids such as alanine, aspartate, glutamate, methionine, proline, and lysine; c) the strains specialized for cloning purpose were spread out from one another; and d) the strains originating from B strain were characterized by succinate accumulation. This work shows that 2D‐NMR can be applied to identify a strain from metabolite analysis, offering a possible alternative to genetic analysis to identify E. coli strains. 相似文献
10.
11.
The association of two gramicidin A (gA) peptides via H-bonds in lipid bilayers causes the formation of an ion channel that
is selective for monovalent cations only. In this study, two gAs were covalently linked with a dioxolane group (SS dimer).
Some functional properties of natural gA channels were compared to that synthetic dimer in Na+- or Cs+-containing solutions. The SS dimer remained in the open configuration most of the time, while natural gA channels had a relatively
brief mean open time. Single channel conductances to Na+ (g
Na
) or Cs+ (g
Cs
) in the SS dimer were smaller than in natural gA. However, g
Na
was considerably more attenuated than g
Cs
. This probably results from a tight solvation of Na+ by the dioxolane linker in the SS channel. In Cs+ solutions, the SS had frequent closures. By contrast, in Na+ solutions the synthetic dimer remained essentially in the open state. The mean open times of SS channels in different solutions
(T
open,Na
> T
open,Cs
> T
open,H
) were inversely proportional to the single channel conductances (g
H
> g
Cs
> g
Na
). This suggests that ion occupancy inside the pore stabilizes the open configuration of the gA dimer. The mean closed time
of the SS dimer was longer in Cs+ than in H+ solutions. Possible mechanisms for these effects are discussed.
Received: 17 September 1999/Revised: 21 December 1999 相似文献
12.
The Mls locus was originally defined to have four alleles; three controlled products that were detectable in primary mixed leukocyte reactions (MLR), whereas one, b, was described as being null. Recently, other investigators postulated that the Mls locus is nonpolymorphic, being composed of the b null allele and of a singly expressed allele previously thought to be the a and d alleles. We previously reported that products controlled by Mls
aand Mls
dwere antigenically distinct and therefore are not controlled by the same allele, and the product of Mls
bon cells of three different strains was easily detectable by Mls
aand Mls
dresponding cells. Thus the b allele is not null. In the present report evidence is presented which indicates that both Mls
band Mls
cencoded products were undetectable by MLR when in the presence of Mls
aor Mls
d. This was demonstrated by (a) the inability of Mls
a/Mls
cand Mls
a/Mls
bF1 cells to stimulate Mls
aresponding cells and Mls
d/Mls
cand Mls
d/Mls
bcells to stimulate Mls
dcells; (b) the positive response of Mls
a/Mls
band Mls
d/Mls
bF1-hybrid cells to Mls
b-encoded products; and (c) the reactivity of Mls
a/Mls
cand Mls
d/Mls
cF1 hybrid cells to Mls
c-encoded determinants. 相似文献
13.
Nick V. Grishin Andrei L. Osterman Elizabeth J. Goldsmith Margaret A. Phillips 《Proteins》1996,24(2):272-273
Trypanosoma brucei ornithine decarboxylase, expressed and purified from E. coli, has been crystallized by the vapor diffusion method using PEG 3350 as a precipitant. The crystals belong to the monoclinic space group P21 and have cell constants of a = 66.3 Å, b = 151.8 Å, c = 83.7 Å, and β = 101.2°. While larger crystals are twinned, smaller crystals (0.4 × 0.3 × 0.05 mm3) are single. 相似文献
14.
15.
《Bioscience, biotechnology, and biochemistry》2013,77(7):1418-1421
Mutant strains of Escherichia coli lacking DsbA, DsbB, or DsbD (proteins required for disulfide bond formation in the periplasm) did not produce mitochondrial or chloroplast cytochromes c, as previously observed for bacterial ones. Unexpectedly, however, cytochrome c 555 (AA c 555) from a hyperthermophile, Aquifex aeolicus, was produced in the E. coli periplasm without Dsb proteins, three times more than with them. These results indicate that the Dsb proteins are not necessarily required for AA c 555 production in E. coli, possibly because of hyperthermophilic origin compared with the others. 相似文献
16.
Summary The early transient current-voltage relationship was measured in internally perfused voltage clamped squid giant axons with various concentrations of sodium on the two sides of the membrane. In the absence of sodium on either side there is an outward transient current which is blocked by tetrodotoxin and varies with internal potassium concentration. The current increases linearly with voltage for positive potentials. Adding sodium ions internally increases the slope of the current-voltage relationship. Adding sodium ions externally also increases the slope between +10 and +80 mV. Adding sodium to both sides produces the sum of the two effects.The current-voltage relationships were fit by straight lines between +10 and +80 mV. Plotting the extrapolated intercepts with the current axis against the differences in sodium concentrations gave a straight line,I
o
=–P(c
o
–c
i
)F.P, the Fickian permeability, is about 10–4 cm/sec. Plotting the slopes in three dimensions against the two sodium concentrations gave a planeg=g
o
+(aNa
o
+bNa
i
)F.a is about 10–6 cm/mV-sec andb about 3×10–6 cm/mV-sec. Thus the current-voltage relationship for the sodium current is well described byI=–P(c
o
–c
i
)F+(ac
o
+bc
i
)FV for positive potentials. This is the linear sum of Fick's Law and Ohm's Law.P/(a+b)=25±1 mV (N=6) and did not vary with the absolute magnitude of the currents. Within experimental error this is equal tokT/e orRT/F.Increasing temperature increasedP, a andb proportionately. Adding external calcium, lithium, or Tris selectively decreasedP anda without changingb. In the absence of sodium, altering internal and external potassium while observing the early transient currents suggests this channel is more asymmetric in its response to potassium than to sodium. 相似文献
17.
Robert H. Fillingame 《Journal of bioenergetics and biomembranes》1992,24(5):485-491
The F0 sector of the ATP synthase complex facilitates proton translocation through the membrane, and via interaction with the F1 sector, couples proton transport to ATP synthesis. The molecular mechanism of function is being probed by a combination of mutant analysis and structural biochemistry, and recent progress on theEscherichia coli F0 sector is reviewed here. TheE. coli F0 is composed of three types of subunits (a, b, andc) and current information on their folding and organization in F0 is reviewed. The structure of purified subunitc in chloroform-methanol-H2O resembles that in native F0, and progress in determining the structure by NMR methods is reviewed. Genetic experiments suggest that the two helices of subunitc must interact as a functional unit around an essential carboxyl group as protons are transported. In addition, a unique class of suppressor mutations identify a transmembrane helix of subunita that is proposed to interact with the bihelical unit of subunitc during proton transport. The role of multiple units of subunitc in coupling proton translocation to ATP synthesis is considered. The special roles of Asp61 of subunitc and Arg210 of subunita in proton translocation are also discussed. 相似文献
18.
Diffusion of tetracycline across the outer membrane of Escherichia coli K-12: involvement of protein Ia. 总被引:4,自引:0,他引:4
The possibility that passage of tetracycline across the outer membrane of K-12 is controlled by one or more of the proteins Ia, Ib and II1 (Henning's nomenclature) was investigated. A mutant lacking protein Ia (obtained by selection for resistance to phage TuIa) was more resistant to tetracycline than wild-type strains or those lacking only proteins Ib or II1. The envelope protein composition of a tetracycline-resistant mutant () was altered in several respects, but the major change involved loss of protein Ia. These data support our previous suggestion [12] that tetracycline diffuses across the outer membrane through hydrophilic regions. Furthermore, they imply that only protein Ia plays a significant role in the passage of this antibiotic across the outer membrane. 相似文献
19.
Judith E. Miller Keith C. Backman Mary Jane O'Connor Randolph T. Hatch 《Journal of industrial microbiology & biotechnology》1987,2(3):143-149
Summary Isogenic strains ofEscherichia coli were grown aerobically in minimal medium in a 2-liter airlift fermentor to determine whether appc (phosphoenolpyruvate carboxylase) mutation had the effect of directing glucose carbon into phenylalanine synthesis. Two host strains, YMC9 (ppc
+) and KB285 (ppc
–) were used, either with (Phec) or without (Phe0) a plasmid which determines constitutive phenylalanine production. Carbon consumption and metabolic products were monitored. Phenylalanine production occurred only in strains carrying the Phec plasmid.ppc
– strains produced less cell mass and more acetate, pyruvate, and phenylalanine (in the Phec strains) than did isogenicppc
+ strains. Lactate and ethanol production were not detected in any of the strains. Phec strains produced less acetate and pyruvate than their Phe0 homologs. Importantly,ppc
–/Phec produced at least six times as much phenylalanine (0.32 g phenylalanine/g dry weight cells) asppc
+/Phec. Even in this case, however, phenylalanine was produced at ten-fold lower levels than acetate. Thus, although theppc
– mutation stimulates phenylalanine production, it also stimulates the production of unwanted by-products such as acetate and pyruvate. 相似文献
20.
Abstract: We have suggested recently the existence of three subtypes of B2 bradykinin receptors in tissues of guinea pigs. We have classified these B2 bradykinin receptors into B2a, B2b, and B2c subtypes depending on their affinity for various bradykinin antagonists. Because the actions of bradykinin in different cell systems appear to be both dependent on and independent of G proteins, we sought to determine whether the binding of [3H]bradykinin to the B2 subtypes is sensitive to guanine nucleotides and, therefore, possibly coupled to G proteins. In the ileum, where we have demonstrated B2a and B2b subtypes, specific [3H]bradykinin binding was reduced with GDP (100 μM) and the nonmetabolized analogue of GTP, guanyl-5′-yl-imidodiphosphate (GppNHp; 100 μM). Competition studies with bradykinin and with [Hyp3]-bradykinin, which shows approximately 20-fold greater selectivity for the B2a subtype than bradykinin, were performed in the presence or absence of GppNHp (100 μM). The competition experiments demonstrated that binding to the B2a subtype, which has higher affinity for [Hyp3]-bradykinin and bradykinin than the B2b subtype, was lost in the presence of GppNHp, whereas binding to the B2b subtype was unaffected. In contrast, GppNHp (100 μM) and GDP (100 μM) failed to alter specific [3H]bradykinin binding to B2b and B2c subtypes in lung. [3H]Bradykinin binding was unaffected by AMP, ADP, ATP, and GMP (100 μM each). Based on this evidence, we suggest that the B2a bradykinin subtype is coupled to G proteins. The B2b and B2c subtypes are either not coupled to G proteins, or may be coupled to the Go-type GTP binding proteins, which have been suggested to be less sensitive to guanine nucleotides. These data provide further evidence for three subtypes of B2-type bradykinin receptors in guinea pig. 相似文献