Metal from metallothionein

Misra, R.R., J.F. Hochadel, G.T. Smith, J.C. Cook, M.P. Waalkes and D.A. Wink. Evidence that nitric oxide enhances cadmium toxicity by displacing the metal from metallothionein. Chem. Res. Toxicol. 9 326-332, 1996. 

Figure 10. Displacements of metal from metallothionein in rat hepatic cytosol. Fractionation of a, cytosol from rat administered Na AuTM in vivo b, cytosol from a that was incubated with 112 i g of Cd for 24 h. 2-Mercaptoethanol was added to the cytosol to prevent air oxidation. Conditions Sephadex G-7S-120 column (2.5 X 100 cm) eluted with 5/nM Tris—HCl, pH 7.8 at 20 mL/hr 9 mL...

Intracellular distribution of essential transition metals is mediated by specific metallochaperones and transporters localized in endomembranes. In other words, the major processes involved in hyperaccumulation of trace metals from the contaminated medium to the shoots by hyperaccumulators as proposed by Yang et al. (2005) include bioactivation of metals in the rhizosphere through root-microbial interaction enhanced uptake by metal transporters in the plasma membranes detoxification of metals by distributing metals to the apoplasts such as binding to cell walls and chelation of metals in the cytoplasm with various ligands (such as PCs, metallothioneins, metal-binding proteins) and sequestration of metals into the vacuole by tonoplast-located transporters. 

Trace metal disturbances may be due to the uremia per se. Indeed, as the urinary excretion route is an important pathway of elimination of many trace elements, i.e. silicon, strontium, aluminum,... impairment of the kidney will be an important determinant of their accumulation, whilst in the presence of a reabsorptive defect a number of trace elements, especially those that are reabsorbed because of their essential role, be lost resulting in a deficient state. The presence of proteinuria may reasonably result in losses of protein bound elements. It has also been shown also that residual renal funchon may importantly alter the accumulation and hence toxic effects of aluminum [2]. In uremia translocation of a particular metal from one tissue to another may also occur. As an example, under normal circumstances the kidney is an important target organ for cadmium. In chronic renal failure however, possibly as a consequence of a reduction in binding proteins (e.g. metallothionein), the concentrahon of cadmium in this tissue decreases to extremely low levels which... 

For -t-2 cations such as zinc(II) and cadmium(ll) each metallothionein molecule contains up to seven metal atoms. X-ray studies indicate that the metal atoms are in approximately tetrahedral sites bound to the cysteine sulfur atoms. The soft mer-cury(II) ion has a higher affinity for sulfur and will displace cadmium from metallothionein. At first the mercury ions occupy tetrahedral sites but as the number increases, the geometries of the metal sites and protein change until about nine Hg(Il) atoms are bound in a linear (S—Hg—S) fashion.92 Up to twelve + 1 cations such as copper(l) and silver(I) can bind per molecule, indicating a coordination number lower than four, probably three (see Problem 12.34),... 

Baer, K.N. and P. Thomas. Isolation of novel metal-binding proteins distinct from metallothionein from spotted seatrout (Cynoscion nebulosus) and Atlantic croaker (Micropogonias undulatus) ovaries. Mar. Biol. 108 31-37, 1991. 

The physiological role of metallothioneins remains unknown, but it may be, in part, to protect cells from metal toxicity by binding metal ions. Metallothioneins may also be important for intestinal and renal absorption of metals and for metal storage and excretion. 

Wang H, Li H, Cai B et al (2008) The effect of nitric oxide on metal release from metallothionein-3 gradual unfolding of the protein. J Biol Inorg Chem 13 411 19... 

E. Mixed in vivo/in vitro Experiments. The same liver cytosol preparations as above were used to study metal displacements from metallothionein by adding gold to the in vivo Cd treated cytosol and vice versa. These experiments more nearly reproduce the situation when metallothionein is presented with gold(I) in the cellular milieu than do the experiments with pure equine renal MT. The resulting chromatograms are shown in Figures 10b and lib, and the metal contents of the metallothionein peaks are given in Table IV. 

Metal Displacements from Metallothionein in Rat Liver Cytosol by In Vitro Addition of Metal... 

When researching fields of study across the toxicological disciplines, I have often been left wondering, Why didn t someone tell me that before For example, it was not immediately obvious to me that transporter proteins and metallothioneins cannot readily be distinguished from metals from the same family, or column within the periodic table. I had to come to that realization over time. Likewise, the fundamental role that lipophilicity and biotransformation play in toxicology was not readily apparent but became evident only after I had been wrestling with these concepts. With this book, I want to bring those ideas to the forefront, not just to scientists and students, but to the interested layman as well. 

Xu M, Wu Y, Wang J, Zhou F (2006) Electrochanistry of and redox-induced metal release from metallothioneins at a nafion-coated bismuth film electrode. Electroanalysis 18 2099-2105... 

Xu, C. (1993). cDNA cloning of a mouse factor that activates transcription from a metal response element of the mouse metallothionein-1 gene in yeast. DNA Cell Biol. 12, 517-525. 

Gardea-Torresdey JL, Arenas NMC, Francisco KJ et al (1998) Ability of immobilized cyanobacteria to remove metal ions from solution and demonstration of the presence of metallothionein genes in various strains. J Hazard Subst Res 1 1-8... 

Birds are comparatively resistant to the biocidal properties of cadmium. Adult drake mallards (Anas platyrhynchos) fed up to 200 mg cadmium per kg diet for 90 days all survived with no loss of body weight (White and Linley 1978). Laying hens fed 200 mg Cd/kg diet also survived egg production was suppressed at that concentration but not at lower concentrations (White and Linley 1978). Marine and terrestrial animals, including ducks, have been shown to be particularly abundant in a wildlife community associated with a marine sewer outfall (Brown et al. 1977). These animals were contaminated with high levels of cadmium, as well as zinc and copper, but were apparently protected from the deleterious effects of high metal body burdens by metallothioneins. Amounts... 

Benson, W.H. and W.J. Birge. 1985. Heavy metal tolerance and metallothionein induction in fathead minnows results from field and laboratory investigations. Environ. Toxicol. Chem. 4 209-217. 

Hylland, K., C. Haux, and C. Hogstrand. 1992. Hepatic metallothionein and heavy metals in dab Limanda limanda from the German Bight. Mar. Ecol. Prog. Ser. 91 89-96. 

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