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1.
Metallothioneins (MTs) are ubiquitous, low molecular mass and cysteine-rich proteins that play important roles in maintaining intracellular metal homeostasis, eliminating metal toxification and protecting the cells against oxidative damages. MTs are able to bind metal ions through the thiol groups of their cysteine residues. Plants have several MT isoforms which are classified into four types based on the arrangement of cysteine residues. In the present study, a rice (Oryza sativa) gene encoding type 1 MT isoform, OsMTI-1b, was inserted in vector pET41a and overexpressed in Escherichia coli as carboxy-terminal extensions of glutathione-S-transferase (GST). The recombinant protein GST-OsMTI-1b was purified using affinity chromatography and its ability to bind with Ni2+, Cd2+, Zn2+ and Cu2+ ions was analyzed. The results demonstrated that this isoform has ability to bind Ni2+, Cd2+ and Zn2+ ions in vitro, whereas it has no substantial ability to bind Cu2+ ions. From competitive reaction with 5,5′-dithiobis(2-nitrobenzoic acid), DTNB, the affinity of metal ions for recombinant form of GST-OsMTI-1b was as follows: Ni2+/Cd2+ > Zn2+ > Cu2+ 相似文献
2.
《Bioscience, biotechnology, and biochemistry》2013,77(12):2650-2656
An acidophilic volvocine flagellate, Chlamydomonas acidophila (Volvocales) that was isolated from an acid lake, Katanuma, in Miyagi prefecture, Japan was studied for growth, ultrastructural characterization, and metal tolerance.Chlamydomonas acidophila is obligately photoautotrophic, and did not grow in the cultures containing acetate or citrate even in the light. The optimum pH for growth was 3.5-4.5. To characterize metal tolerance, the toxic effects of Cd, Co, Cu, and Zn on this alga were also studied. Effective metal concentrations, which limited the growth by 50%, EC50 were measured, after 72h of static exposure. EC50s were 14.4 μM Cd2+, 81.3 μM Co2+, 141μM Cu2+, and 1.16 mM Zn2+ for 72 h of exposure. Thus, this alga had stronger tolerance to these metals than other species in the genus Chlamydomonas. 相似文献
3.
I. R. Grin P. G. Konorovsky G. A. Nevinsky D. O. Zharkov 《Biochemistry. Biokhimii?a》2009,74(11):1253-1259
Prokaryotic enzymes formamidopyrimidine-DNA glycosylase (Fpg) and endonuclease VIII (Nei) and their eukaryotic homologs NEIL1,
NEIL2, and NEIL3 define the Fpg family of DNA glycosylases, which initiate the process of repair of oxidized DNA bases. The
repair of oxidative DNA lesions is known to be impaired in vivo in the presence of ions of some heavy metals. We have studied the effect of salts of several alkaline earth and transition
metals on the activity of Fpg-family DNA glycosylases in the reaction of excision of 5,6-dihydrouracil, a typical DNA oxidation
product. The reaction catalyzed by NEIL1 was characterized by values K
m = 150 nM and k
cat = 1.2 min−1, which were in the range of these constants for excision of other damaged bases by this enzyme. NEIL1 was inhibited by Al3+, Ni2+, Co2+, Cd2+, Cu2+, Zn2+, and Fe2+ in Tris-HCl buffer and by Cd2+, Zn2+, Cu2+, and Fe2+ in potassium phosphate buffer. Fpg and Nei, the prokaryotic homologs of NEIL1, were inhibited by the same metal ions as NEIL1.
The values of I50 for NEIL1 inhibition were 7 μM for Cd2+, 16 μM for Zn2+, and 400 μM for Cu2+. The inhibition of NEIL1 by Cd2+, Zn2+, and Cu2+ was at least partly due to the formation of metal-DNA complexes. In the case of Cd2+ and Cu2+, which preferentially bind to DNA bases rather than phosphates, the presence of metal ions caused the enzyme to lose the
ability for preferential binding to damaged DNA. Therefore, the inhibition of NEIL1 activity in removal of oxidative lesions
by heavy metal ions may be a reason for their comutagenicity under oxidative stress. 相似文献
4.
Functional role of cellular prion protein (PrPc) has been hypothesized to be in metal homeostasis and providing cells with a superoxide dismutase (SOD)-like activity to escape damage by reactive oxygen species (ROS). PrPc interacts with a range of divalent metal ions and undergoes Cu2+ as well as Zn2+-associated endocytosis, thereby maintaining homeostasis of these and other metal ions. Conformational change to a β-sheet rich, protease resistant entity, reminiscent of the disease-associated scrapie form called PrPsc, has been found to be induced by interaction of PrPc with metal ions like Cu2+, Zn2+, Mn2+ and Fe2+. This review compiles data from various experimental studies of the interaction of metals with PrPc. The effect of metal ions on the expression and conformation of the prion protein is described in detail with emphasis on their possible physiological and pathogenic role. Further, a hypothesis is presented where attainment of altered conformation by metal-bound PrPc has been viewed as a deleterious consequence of efforts made by cells to maintain metal homeostasis. Thus, PrPc presumably sacrifices itself by converting into PrPsc form in an attempt to protect cells from the toxicity of metal imbalance. Finally, possible reasons for contradictions reported in the literature on the subject are explored and experimental approaches to resolve the same are suggested. 相似文献
5.
The absorption of Ni2+ by 21-day-old soybean plants (Glycine max cv. Williams) was investigated with respect to its concentration dependence, transport kinetics, and interactions with various nutrient cations. Nickel absorption, measured as a function of concentration (0.02 to 100 μm), demonstrated the presence of multiple absorption isotherms. Each of the three isotherms conforms to Michaelis-Menten kinetics; kinetic constants are reported for uptake by the intact plant and for transfer from root to shoot tissues. The absorption of Ni2+ by the intact plant and its transfer from root to shoot were inhibited by the presence of Cu2+, Zn2+, Fe2+, and Co2+. Competition kinetic studies showed Cu2+ and Zn2+ to inhibit Ni2+ absorption competitively, suggesting that Ni2+, Cu2+, and Zn2+ are absorbed using the same carrier site. Calculated Km and Ki constants for Ni2+ in the presence and absence of Cu2+ were 6.1 and 9.2 μm, respectively, whereas Km and Ki constants were calculated to be 6.7 and 24.4 μm, respectively, for Ni2+ in the presence and absence of Zn2+. The mechanism of inhibition of Ni2+ in the presence of Fe2+ and Co2+ was not resolved by classical kinetic relationships. 相似文献
6.
Illing AC Shawki A Cunningham CL Mackenzie B 《The Journal of biological chemistry》2012,287(36):30485-30496
Divalent metal-ion transporter-1 (DMT1) is a H+-coupled metal-ion transporter that plays essential roles in iron homeostasis. DMT1 exhibits reactivity (based on evoked currents) with a broad range of metal ions; however, direct measurement of transport is lacking for many of its potential substrates. We performed a comprehensive substrate-profile analysis for human DMT1 expressed in RNA-injected Xenopus oocytes by using radiotracer assays and the continuous measurement of transport by fluorescence with the metal-sensitive PhenGreen SK fluorophore. We provide validation for the use of PhenGreen SK fluorescence quenching as a reporter of cellular metal-ion uptake. We determined metal-ion selectivity under fixed conditions using the voltage clamp. Radiotracer and continuous measurement of transport by fluorescence assays revealed that DMT1 mediates the transport of several metal ions that were ranked in selectivity by using the ratio Imax/K0.5 (determined from evoked currents at −70 mV): Cd2+ > Fe2+ > Co2+, Mn2+ ≫ Zn2+, Ni2+, VO2+. DMT1 expression did not stimulate the transport of Cr2+, Cr3+, Cu+, Cu2+, Fe3+, Ga3+, Hg2+, or VO+. 55Fe2+ transport was competitively inhibited by Co2+ and Mn2+. Zn2+ only weakly inhibited 55Fe2+ transport. Our data reveal that DMT1 selects Fe2+ over its other physiological substrates and provides a basis for predicting the contribution of DMT1 to intestinal, nasal, and pulmonary absorption of metal ions and their cellular uptake in other tissues. Whereas DMT1 is a likely route of entry for the toxic heavy metal cadmium, and may serve the metabolism of cobalt, manganese, and vanadium, we predict that DMT1 should contribute little if at all to the absorption or uptake of zinc. The conclusion in previous reports that copper is a substrate of DMT1 is not supported. 相似文献
7.
Macroalgae have received much attention for heavy metal removal in treatment of domestic wastewater. In this report, the uptake capacity of a common freshwater green alga, Cladophora fracta, for heavy metal ions (copper, zinc, cadmium, and mercury) was evaluated. The equilibrium adsorption capacities were 2.388?mg Cu2+, 1.623?mg Zn2+, 0.240?mg Cd2+, and 0.228?mg Hg2+ per gram of living algae at 18°C and pH?5.0. The removal efficiency for Cu2+, Zn2+, Cd2+, and Hg2+ were 99, 85, 97, and 98%, respectively. Greater removal efficiency was achieved when the concentrations of metal ions were at very low level. The results indicated that living algae are suitable for removal and recovery of heavy metal ions from aqueous solutions and can be a potential tool to treat industrial wastewater. 相似文献
8.
The present work deals with the biosorption performance of dried and non-growing biomasses of Exiguobacterium sp. ZM-2, isolated from soil contaminated with tannery effluents, for the removal of Cd2+, Ni2+, Cu2+, and Zn2+ from aqueous solution. The metal concentrations studied were 25 mg/l, 50 mg/l, 100 mg/l, 150 mg/l and 200 mg/l. The effect of solution pH and contact time was also studied. The biosorption capacity was significantly altered by pH of the solution. The removal of metal ions was conspicuously rapid; most of the total sorption occurred within 30 min. The sorption data have been analyzed and fitted to the Langmuir and Freundlich isotherm models. The highest Qmax value was found for the biosorption of Cd2+ at 43.5 mg/g in the presence of the non-growing biomass. Recovery of metals (Cd2+, Zn2+, Cu2+ and Ni2+) was found to be better when dried biomass was used in comparison to non-growing biomass. Metal removal through bioaccumulation was determined by growing the bacterial strain in nutrient broth amended with different concentrations of metal ions. This multi-metal resistant isolate could be employed for the removal of heavy metals from spent industrial effluents before discharging them into the environment. 相似文献
9.
Kerem Uzun Emre Çevik Mehmet Şenel Abdülhadi Baykal 《Bioprocess and biosystems engineering》2013,36(12):1807-1816
Polyvinylimidazole (PVI)-grafted iron oxide nanoparticles (PVIgMNP) were prepared by grafting of telomere of PVI on the iron oxide nanoparticles. Different metal ions (Cu2+, Zn2+, Cr2+, Ni2+) ions were chelated on polyvinylimidazole-grafted iron oxide nanoparticles, and then the metal-chelated magnetic particles were used in the adsorption of invertase. The maximum invertase immobilization capacity of the PVIgMNP–Cu2+ beads was observed to be 142.856 mg/g (invertase/PVIgMNP) at pH 5.0. The values of the maximum reaction rate (V max) and Michaelis–Menten constant (Km) were determined for the free and immobilized enzymes. The enzyme adsorption–desorption studies, pH effect on the adsorption efficiency, affinity of different metal ions, the kinetic parameters and storage stability of free and immobilized enzymes were evaluated. 相似文献
10.
11.
Interactions between metal ions and amino acids are common both in solution and in the gas phase. The effect of metal ions and water on the structure of l-histidine is examined. The effect of metal ions (Li+, Na+, K+, Mg2+, Ca2+, Ni2+, Cu2+ and Zn2+) and water on structures of His·M(H2O)m, m = 0.1 complexes have been determined theoretically employing density functional theories using extended basis sets. Of the five stable complexes investigated the relative stability of the gas-phase complexes computed with DFT methods (with one exception of K+ systems) suggest metallic complexes of the neutral l-histidine to be the most stable species. The calculations of monohydrated systems show that even one water molecule has a profound effect on the relative stability of individual complexes. Proton dissociation enthalpies and Gibbs energies of l-histidine in the presence of the metal cations Li+, Na+, K+, Mg2+, Ca2+, Ni2+, Cu2+ and Zn2+ were also computed. Its gas-phase acidity considerably increases upon chelation. Of the Lewis acids investigated, the strongest affinity to l-histidine is exhibited by the Cu2+ cation. The computed Gibbs energies ΔG are negative, span a rather broad energy interval (from ?130 to ?1,300 kJ/mol), and upon hydration are appreciably lowered. 相似文献
12.
Prerana Gogoi Monika Chandravanshi Suraj Kumar Mandal Ambuj Srivastava 《Journal of biomolecular structure & dynamics》2016,34(7):1470-1485
About one-third of the existing proteins require metal ions as cofactors for their catalytic activities and structural complexities. While many of them bind only to a specific metal, others bind to multiple (different) metal ions. However, the exact mechanism of their metal preference has not been deduced to clarity. In this study, we used molecular dynamics (MD) simulations to investigate whether a cognate metal (bound to the structure) can be replaced with other similar metal ions. We have chosen seven different proteins (phospholipase A2, sucrose phosphatase, pyrazinamidase, cysteine dioxygenase (CDO), plastocyanin, monoclonal anti-CD4 antibody Q425, and synaptotagmin 1 C2B domain) bound to seven different divalent metal ions (Ca2+, Mg2+, Zn2+, Fe2+, Cu2+, Ba2+, and Sr2+, respectively). In total, 49 MD simulations each of 50 ns were performed and each trajectory was analyzed independently. Results demonstrate that in some cases, cognate metal ions can be exchanged with similar metal ions. On the contrary, some proteins show binding affinity specifically to their cognate metal ions. Surprisingly, two proteins CDO and plastocyanin which are known to bind Fe2+ and Cu2+, respectively, do not exhibit binding affinity to any metal ion. Furthermore, the study reveals that in some cases, the active site topology remains rigid even without cognate metals, whereas, some require them for their active site stability. Thus, it will be interesting to experimentally verify the accuracy of these observations obtained computationally. Moreover, the study can help in designing novel active sites for proteins to sequester metal ions particularly of toxic nature. 相似文献
13.
A spectrophotometric method for the determination of zinc, copper, and cobalt ions in metalloproteins using Zincon 总被引:1,自引:0,他引:1
Crystal E. Säbel 《Analytical biochemistry》2010,397(2):218-1966
Zincon (2-carboxy-2′-hydroxy-5′-sulfoformazylbenzene) has long been known as an excellent colorimetric reagent for the detection of zinc and copper ions in aqueous solution. To extend the chelator’s versatility to the quantification of metal ions in metalloproteins, the spectral properties of Zincon and its complexes with Zn2+, Cu2+, and Co2+ were investigated in the presence of guanidine hydrochloride and urea, two common denaturants used to labilize metal ions in proteins. These studies revealed the detection of metals to be generally more sensitive with urea. In addition, pH profiles recorded for these metals indicated the optimal pH for complex formation and stability to be 9.0. As a consequence, an optimized method that allows the facile determination of Zn2+, Cu2+, and Co2+ with detection limits in the high nanomolar range is presented. Furthermore, a simple two-step procedure for the quantification of both Zn2+ and Cu2+ within the same sample is described. Using the prototypical Cu2+/Zn2+-protein superoxide dismutase as an example, the effectiveness of this method of dual metal quantification in metalloproteins is demonstrated. Thus, the spectrophotometric determination of metal ions with Zincon can be exploited as a rapid and inexpensive means of assessing the metal contents of zinc-, copper-, cobalt-, and zinc/copper-containing proteins. 相似文献
14.
Hiroshi Maeda Juníchi Nakajima Kazuki Oka Kenta Ooi Shoichi Ikeda 《International journal of biological macromolecules》1982,4(6):352-356
The effects of divalent ions on fully charged ) have been examined using circular dichroism for eight species: CuCl2, CdCl2, ZnCl2, NiCl2, CoCl2, BaCl2, CaCl2, and MgCl2. Five of them are effective inducers of β-form in the order: Cu2+Cd2+Zn2+Ni2+Co2+, in media with no salt added. However, the other three ions (Ba2+, Ca2+ and Mg2+), are not effective. Precipitation occurs when metal chlorides reach the vicinity of the equivalent point except for Ca2+ and Mg2+. Precipitation of the random coil form is slow, while that of the β-form is rapid. Addition of NcCl reduces the solubility of the β-form considerably. The pH value varies linearly with the logarithm of metal chloride concentration CM for Ba2+, Ca2+ and Mg2+ ions, while nonlinear dependence of pH on log CM is found for Cu2+, Ni2+ and Co2+ ions. 相似文献
15.
Topochemical factors in potentiation of contraction by heavy metal cations 总被引:5,自引:1,他引:4
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In addition to the previously studied Zn2+, low concentrations (about 0.5 mM) of Be2+, Ba2+, Cd2+, Ni2+, Cu2+, Pt4+ and, outstandingly, 0.5 µM of UO2
2+, potentiate the twitch of frog sartorius and toe muscles by prolonging the active state of contraction. The degree of potentiation is a roughly S-shaped function of p(metal2+), suggesting that each metal binds to a ligand of the muscle fiber, representative apparent affinity constants being: UO2
2+, 5 x 106; Zn2+, 2.8 x 105; and Cd2+, 2 x 104. UO2
2+ potentiation effects are rapidly reversed by PO4, and Zn2+ and Cd2+ effects by EDTA, PO4, and cysteine. The rapidity of these reversals by the nonpenetrating EDTA and PO4, and the fact that heavy metal ions evidently potentiate by prolonging the action potential, indicate that the metal potentiators exert their primary action at readily accessible (i.e. plasma and T tubular) membrane sites. The relatively slow kinetics of development of potentiation, and the even slower reversal of it in pure Ringer''s solution, indicate that the metal ions are bound to connective tissue, as well as to muscle fibers. The binding effects at the readily accessible membrane sites evidently impairs delayed rectification and thus modifies the action potential and excitation-contraction coupling so as to cause potentiation. SH is excluded, and PO4 and imidazole are possibilities, as the membrane ligand binding the potentiating metal ions. 相似文献
16.
The stability of the hemopexin-heme (Hx-heme) complex to dissociation of the heme prosthetic group has been examined in bicarbonate buffers in the presence and absence of various divalent metal ions. In NH4HCO3 buffer (pH 7.4, 20 mm, 25 °C) containing Zn2+ (100 μm), 14% of the heme dissociates from this complex (4.5 μm) within 10 min, and 50% dissociates within 2 h. In the absence of metal ions, the rate of dissociation of this complex is far lower, is decreased further in KHCO3 solution, and is minimal in NaHCO3. In NH4HCO3 buffer, dissociation of the Hx-heme complex is accelerated by addition of divalent metals with decreasing efficiency in the order Zn2+ > Cu2+ ≫ Ni2+ > Co2+≫Mn2+. Addition of Ca2+ prior to addition of Zn2+ stabilizes the Hx-heme complex to dissociation of the heme group, and addition of Ca2+ after Zn2+-induced dissociation of the Hx-heme complex results in re-formation of the Hx-heme complex. These effects are greatly accelerated at 37 °C and diminished in other buffers. Overall, the solution conditions that promote formation of the Hx-heme complex are similar to those found in blood plasma, and conditions that promote release of heme are similar to those that the Hx-heme complex should encounter in endosomes following endocytosis of the complex formed with its hepatic receptor. 相似文献
17.
Effect of heavy metal ions on growth and biochemical characteristics of photosynthesis of barley and maize seedlings 总被引:1,自引:0,他引:1
The effects of Cu2+, Zn2+, Cd2+ and Pb2+ on growth and the biochemical characteristics of photosynthesis were more expressed in barley (Hordeum vulgare L.) than in maize (Zea mays L.) seedlings. The barley and maize seedlings exhibited retardation in shoot and root growth after exposure of Cu2+, Cd2+ and Pb2+. The Zn2+ions practically did not influence these characteristics. The total protein content of barley and maize roots declined with an increase in heavy metal ion concentrations. The protein content of barley shoots was only slighly decreased with an increase in heavy metal ion concentrations, but the protein content in maize shoots was increased under the same conditions. The chlorophyll content was decreased in barley shoots and increased in maize. The ribulose-l,5-bisphosphate carboxylase (RuBPC, EC 4.1.1.39) and phosphoenolpyruvate carboxylase (PEPC, EC 4.1.1.31) activities were decreased drastically by Cu2+, Cd2+ and Pb2+ in thein vivo experiments. The tested heavy metal ions affect photosynthesis probably mainly by inhibition of these key carboxylating enzymes: this mechanism was studied in thein vitro experiments. 相似文献
18.
The metal ions Zn2+, Cu2+, and Fe2+ play a significant role in the aggregation mechanism of Aβ peptides. However, the nature of binding between metal and peptide has remained elusive; the detailed information on this from the experimental study is very difficult. Density functional theory (dft) (M06‐2X/6‐311++G (2df,2pd) +LANL2DZ) has employed to determine the force field resulting due to metal and histidine interaction. We performed 200 ns molecular dynamics (MD) simulation on Aβ1‐42‐Zn2+, Aβ1‐42‐Cu2+, and Aβ1‐42‐Fe2+ systems in explicit water with different combination of coordinating residues including the three Histidine residues in the N‐terminal. The present investigation, the Aβ1‐42‐Zn2+ system possess three turn conformations separated by coil structure. Zn2+ binding caused the loss of the helical structure of N‐terminal residues which transformed into the S‐shaped conformation. Zn2+ has reduced the coil and increases the turn content of the peptide compared with experimental study. On the other hand, the Cu2+ binds with peptide, β sheet formation is observed at the N‐terminal residues of the peptide. Fe2+ binding is to promote the formation of Glu22‐Lys28 salt‐bridge which stabilized the turn conformation in the Phe19‐Gly25 residues, subsequently β sheets were observed at His13‐Lys18 and Gly29‐Gly37 residues. The turn conformation facilitates the β sheets are arranged in parallel by enhancing the hydrophobic contact between Gly25 and Met35, Lys16 and Met35, Leu17 and Leu34, Val18 and Leu34 residues. The Fe2+ binding reduced the helix structure and increases the β sheet content in the peptide, which suggested, Fe2+ promotes the oligomerization by enhancing the peptide‐peptide interaction. Proteins 2016; 84:1257–1274. © 2016 Wiley Periodicals, Inc. 相似文献
19.
Metal ion complexes of d-biotin in solution. Stability of the stereoselective thioether coordination
By spectrophotometry and 1H nmr, several of the stability constants of the thioether complexes between Mg2+, Ca2+, Mn2+, Cu2+, Zn2+, Cd2+, or Ag+ and d-biotin (Bio), tetrahydrothiophene (Tht), and dimethyl sulfide (Dms) have been measured in 50% aqueous ethanol, 96% N,N-dimethylformamide (DMF), 98% d6-dimethyl sulfoxide, or in D2O. With decreasing concentration of water, the thioether interaction increases with the biologically important metal ions, whereas, e.g., Ag+ behaves in the opposite way. The stability of these complexes is, in general, quite small: for example, with d-biotin in 96% DMF (I = 1.0; 25°C) log KM(Bio)M = 0.03 and 1.64 for Cu2+ and Ag+, respectively; in D2O (I = 0.5 for Ag+, all others 2–5; 27°C) log KM(Bio)M ? ?1.0, ?1.4, ?1.2, ?0.9, or 4.20 for Mg2+, Ca2+, Zn2+, Cd2+, or Ag+. In those cases where the difference log KM(Tht)M ? log KM(Bio)M can be calculated, it is in the order of 0.3 log units; this observation, as well as the chemical shifts measured, confirm the earlier suggestion that the interaction at the sulfur of biotin is stereoselective: the metal ion coordinates from “below” the tetrahydrothiophene ring of biotin to the sulfur atom, i.e., trans to the urea ring. It is emphasized that despite the low stability of these complexes with the biologically meaningful metal ions, the extent of the interaction is enough to create specific structures. 相似文献
20.
Rhizopus arrhizus biomass was found to absorb a variety of different metal cations and anions but did not absorb alkali metal ions. The amount of uptake of the cations was directly related to ionic radii of La3+, Mn2+, Cu2+, Zn2+, Cd2+, Ba2+, Hg2+, Pb2+, UO22+, and Ag+. The uptake of all the cations is consistent with absorption of the metals by sites in the biomass containing phosphate, carboxylate, and other functional groups. The uptake of the molybdate and vanadate anions was strongly pH dependent, and it is proposed that the uptake mechanism involves electrostatic attraction to positively charged functional groups. 相似文献