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221.
Metallothionein (MT) is a prominent metal-binding protein and in mammalian systems contains a two-domain βα motif, while in lower life forms MT often consists of only a single-domain structure. There are also unusual MTs from American oysters that consist of multiple domains (from one to four α domains). This report details the study of the As3+-metalation to two different concatenated triple β and α domain MTs using time-resolved electrospray ionization mass spectrometry (ESI MS). Analysis of kinetic ESI MS data show that ααα human MT and βββ human MT bind As3+ in a noncooperative manner and involves up to 11 sequential bimolecular reactions. We report the complete progress of the reactions for the As3+-metalation of both triple-domain MTs from zero and up to 9 (βββ) or 10 As3+ ions (ααα). The rate constants for the As3+-metalation are reported for both the βββ and ααα human MT. At room temperature (298 K) and pH 3.5, the sequential individual rate constants, kn (n = 1-9) for the As3+-metalation of βββhMT starting at k1βββ are 40, 36, 37, 26, 27, 17, 12, 6, and 1 M−1 s−1; while at room temperature (298 K) and pH 3.5, the sequential individual rate constants, kn (n = 1-10) for the As3+-metalation of αααhMT starting at k1ααα are 52, 45, 46, 42, 38, 36, 29, 25, 14, and 6 M−1 s−1. The trend in the rate constant values reported for these two triple-domain MT proteins supports our previous proposal that the rate constant values are proportionally related to the total number of equivalent binding sites. The rate of binding for the 1st As3+ is the fastest we have determined for any MT to date. Additionally, we propose that the data show for the first time for any MT species, that interdomain metalation occurs in the binding of the 10th and 11th As3+ to αααhMT. 相似文献
222.
Jaume Folch Arturo Ortega Maria Cabré José L. Paternáin 《Biological trace element research》1998,63(2):113-121
The monitoring of heavy metals is important if adverse effects on health are to be avoided. In humans, metallothionein (MT)
has been used as a biomonitor for the assessment of cadmium (Cd). In the present study, subjects drawn from the population
of Tarragona Province (NE Spain) were investigated. Urinary MT, zinc (Zn), and copper (Cu) concentrations, corrected for creatine
concentrations, were determined in 625 samples from healthy subjects aged between 10 and 65 yr. Mean values of MT and Cu in
females were higher than those in males, with levels of 29.5 (23.8) vs. 22.7 (24.9) μg MT/creatinine (p<0.001) and 4.8 (6.1) vs 3.4 (4.9) μg Cu/g creatinine (p<0.001). No differences between males and females were observed with respect to urinary Zn: 78.0 (66.4) vs 73.0 (85.5) μg/g
creatinine, respectively (p=0.332). Significantly higher MT, Zn, and Cu values were observed in the females aged 15–19 yr and, in the age group of 50–54
yr, only in the Zn and Cu values, when compared with those in males. Significant positive correlations of MT vs Zn and Cu
as well as correlations of Zn vs Cu levels were observed in both genders. The present findings confirm the proposed role of
MT as a biomonitor of mineral status. 相似文献
223.
224.
Kumar KS Ravi Kumar B Siddavattam D Subramanyam C 《Biochemical and biophysical research communications》2006,345(3):1010-1013
In continuation of our recent observations indicating the presence of a lone calcineurin-dependent response element (CDRE) in the -3730bp upstream region of copper-induced metallothionein (CuMT) gene of Neurospora [K.S. Kumar, S. Dayananda, C. Subramanyam, Copper alone, but not oxidative stress, induces copper-metallothionein gene in Neurospora crassa, FEMS Microbiol. Lett. 242 (2005) 45-50], we isolated and characterized the CDRE-binding protein. The cloned upstream region of CuMT gene was used as the template to specifically amplify CDRE element, which was immobilized on CNBr-activated Sepharose 4B for use as the affinity matrix to purify the CDRE binding protein from nuclear extracts obtained from Neurospora cultures grown in presence of copper. Two-dimensional gel electrophoresis of the affinity purified protein revealed the presence of a single 17kDa protein, which was identified and characterized by MALDI-TOF. Peptide mass finger printing of tryptic digests and analysis of the 17kDa protein matched with the regulatory beta-subunit of calcineurin (Ca(2+)-calmodulin dependent protein phosphatase). Parallel identification of nuclear localization signals in this protein by in silico analysis suggests a putative role for calcineurin in the regulation of CuMT gene expression. 相似文献
225.
Plant metallothionein domains: functional insight into physiological metal binding and protein folding 总被引:6,自引:0,他引:6
Plant metallothioneins (MTs) differ from animal MTs by a peculiar sequence organization consisting of two short cysteine-rich terminal domains linked by a long cysteine-devoid spacer. The role of the plant MT domains in the protein structure and functionality is largely unknown. Here, we investigate the separate domain contribution to the in vivo binding of Zn and Cu and to confer metal tolerance to CUP1-null yeast cells of a plant type 2 MT (QsMT). For this purpose, we obtained three recombinant peptides that, respectively, correspond to the single N-terminal (N25) and C-terminal (C18) cysteine-rich domains of QsMT, and a chimera in which the spacer is replaced with a four-glycine bridge (N25-C18). The metal-peptide preparations recovered from Zn- or Cu-enriched cultures were characterized by ESI-MS, ICP-OES and CD and UV-vis spectroscopy and data compared to full length QsMT. Results are consistent with QsMT giving rise to homometallic Zn- or Cu-MT complexes according to a hairpin model in which the two Cys-rich domains interact to form a cluster. In this model the spacer region does not contribute to the metal coordination. However, our data from Zn-QsMT (but not from Cu-QsMT) support a fold of the spacer involving some interaction with the metal core. On the other hand, results from functional complementation assays in endogenous MT-defective yeast cells suggest that the spacer region may play a role in Cu-QsMT stability or subcellular localization. As a whole, our results provide the first insight into the structure/function relationship of plant MTs using the analysis of the separate domain abilities to bind physiological metals. 相似文献
226.
Chang CC Lee SF Sun KW Ho CC Chen YT Chang CH Kan LS 《Biochemical and biophysical research communications》2006,340(4):1134-1138
Naturally occurring metallothionein (MT) is a metal binding protein, which binds to seven Zn2+ through 20 conserved cysteines and forms two metal binding clusters with a Zinc-Blende structure. We demonstrate that the MT, when substituting the Zn2+ ions by Mn2+ and Cd2+, exhibits magnetic hysteresis loop observable by SQUID from 10 to 330 K. The magnetic moment may have originated from the bridging effect of the sulfur atoms between the metal ions that leads to the alignment of the electron spins of the Mn2+ ions inside the clusters. The protein backbone may restrain the net spin moment of Mn2+ ions from thermal fluctuation. The modified magnetic-metallothionein is a novel approach to creating molecular magnets with operating temperatures up to 330 K. 相似文献
227.
Radical scavenging abilities of fish MT-A and mussel MT-10 metallothionein isoforms: An ESR study 总被引:2,自引:0,他引:2
Buico A Cassino C Dondero F Vergani L Osella D 《Journal of inorganic biochemistry》2008,102(4):921-927
Metallothioneins (MTs) are cysteine-rich proteins involved in homeostasis of essential metals, detoxification of toxic metals and scavenging of free radicals. Scavenging of the stable 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical was measured by means of ESR spectroscopy for two recombinant MTs from aquatic species: MT-10 from the sea mussel Mytilus galloprovincialis, and MT-A from the fish Oncorhyncus mykiss. Both the zinc- and the cadmium-loaded forms (Zn(7)-MTs and Cd(7)-MTs) were analysed, using the commercial MT-II (Zn(7)-MT-II and Cd(7)-MT-II, respectively) from rabbit liver as a reference. A decrease in the scavenging ability was observed for all the three MTs passing from the Zn- to the Cd-loaded forms, because of the higher stability of the Cd-mercapto complex. The Zn(7)-MTs from aquatic species were more effective in scavenging DPPH signal than the rabbit Zn(7)-MT-II (2.8 and 4-folds, respectively). Similar results were obtained also for the Cd(7)-MTs, thus confirming the stronger antioxidant power of MTs from aquatic organisms compared with the rabbit MT-II. Moreover, mussel MT-10 was more active in DPPH scavenging than fish MT-A. When the complete release of metals from MTs was obtained by lowering the pH to 3 or, alternatively, by adding the chelating agent diethylenetriaminepentaacetic acid (DTPA), an increase in the scavenging ability of MTs was observed. 相似文献
228.
Vaclav Diopan Violetta Shestivska Vojtech Adam Tomas Macek Martina Mackova Ladislav Havel Rene Kizek 《Plant Cell, Tissue and Organ Culture》2008,94(3):291-298
Phytoremediation is a process that utilizes plants to remove, transfer, stabilize, or destroy pollutants in soil, sediment,
and groundwater. Plants used for such purposes have several requirements. Genetic engineering these plants could be an effective
tool used to acquire features needed for such purposes within a substantial amount of time. This paper aims to utilize electrochemical
techniques to analyze transgenic tobacco and, thus, to reveal their heavy metals phytoremediation potential. Total thiol and
metallothionein (MT) quantities were determined in the control and transgenic tobacco plants. The total content of thiols
in transgenic plants varied within the range of 561 to 1,671 μg g−1. Furthermore, the determination of MT was done on transgenic tobacco plants. The level of human MT in transgenic tobacco
plants varied between 25 and 95 μg g−1. However, a plant cell protects itself by synthesizing low molecular mass thiols such as reduced glutathione and phytochelatins
to protect itself against heavy metals toxicity. The most important thiols, cysteine (Cys), glutathione (GSH), oxidised glutathione
(GSSG) and phytochelatin 2 (PC2), were determined in the non-transgenic and transgenic tobacco plants by high performance
liquid chromatography with electrochemical detection. Tobacco plants synthesizing the highest amount of metallothionein have
the highest basal level of phytochelatin 2 as well as reduced glutathione and free cysteine. It clearly follows from the results
obtained that the biosynthesis of particular thiols is mutually linked, which contributes to a better protection of a transgenic
plant against heavy metals effects. 相似文献
229.
Zhi-Chun Ding Xin-Chen Teng Qi Zheng Feng-Yun Ni Bin Cai Yang Wang Guo-Ming Zhou Hong-Zhe Sun Xiang-Shi Tan Zhong-Xian Huang 《Biometals》2009,22(5):817-826
Metallothinein-3 (MT3), also named neuronal growth inhibitory factor (GIF), is attractive by its distinct neuronal growth
inhibitory activity, which is not shared by other MT isoforms. The polypeptide chain of GIF is folded into two individual
domains, which are connected by a highly conserved linker, KKS. In order to figure out the significance of the conserved segment,
we constructed several mutants of human GIF (hGIF), including the K31/32A mutant, the K31/32E mutant and the KKS-SP mutant
by site-directed mutagenesis. pH titration and DTNB reaction exhibited that all the three mutations made the β-domain lower in stability and looser. More significantly, change of KKS to SP also altered the general backbone conformation
and metal–thiolate cluster geometry. Notably, bioassay results showed that the bioactivity of the K31/32A mutant and the K31/32E
mutant decreased obviously, while the KKS-SP mutant lost inhibitory activity completely. Based on these results, we proposed
that the KKS linker was a crucial factor in modulating the stability and the solvent accessibility of the Cd3S9 cluster in the β-domain through domain–domain interactions, thus was indispensable to the biological activity of hGIF. 相似文献
230.
Thanh T. Ngu 《Biochemical and biophysical research communications》2010,401(1):69-74
As3+ bound to the two-domain, recombinant human metallothionein (isoform 1a) is stable at pH 7 and translocates via protein-protein interactions to other metallothionein proteins. The data show As3+ transfer from the two-domain β-α-hMT to binding sites in the isolated apo-β-hMT and apo-α-hMT. Under conditions of equilibrium, apo- and partially-metallated species coexist indicating that noncooperative demetallation of the As6-βα-hMT occurrs. As3+ transfer under conditions (pH 7) where the free As3+ ion is not stable, provides evidence that Cd2+ and Zn2+ transfer may also take place through protein-protein interactions and that partially metallated Cd-MT and Zn-MT would be stable. 相似文献