Yeast metallothioneins

Skroch, P., Buchman, C., Karin, M. (1993). Regulation of human and yeast metallothionein gene transcription by heavy metal ions. Prog. Clin. Biol. Res. 380, 113-128. 

Butt, T.R. Ecker, D.J. (1987). Yeast metallothionein and applications to biotechnology. Microbiological Reviews 51, 351-64. 

Winge, D.R., Nielson, K.B., Gray, W.R. Hamer, D.H. (1985). Yeast metallothionein sequence and metal-binding properties. Journal of Biological Chemistry 260, 14464-70. 

Structural and functional studies of the amino terminus of yeast metallothionein. J Biol Chem 262 12912-12919. 

Narula SS, Mehra RK, Winge DR et al (1991) Establishment of the metal-to-cysteine connectivities in silver-substituted yeast metallothionein. J Am Chem Soc 113 9354-9358 Andersen RJ, diTargiani RC, Hancock RD et al (2006) Characterization of the first N2S (alkylthiolate)lead compound a model for three-coordinate lead in biological systems. Inorg Chem 45 6574-6576... 

FIGURE 6. HMQC spectrum of Ag7T48 yeast metallothionein residues 1 -48 from Saccharomyces cerevesiae obtained at 500 MHz with preparation... 

Yeast Metallothionein Gene Function and Regulation by Metal Ions... 

Silar P, Butler G, Thiele DJ (1991) Heat shock transcription factor activates transcription of the yeast metallothionein gene. Mol Cell Biol 11 1232-1238 Squibb KS, Pritchard JB, Fowler BA (1984) Cadmium metallothionein nephropathy ultrastructural/biochemical alterations and intracellular cadmium binding. J Pharmacol Exp Ther 229 311-321... 

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. 

In mammals, as in yeast, several different metallothionein isoforms are known, each with a particular tissue distribution (Vasak and Hasler, 2000). Their synthesis is regulated at the level of transcription not only by copper (as well as the other divalent metal ions cadmium, mercury and zinc) but also by hormones, notably steroid hormones, that affect cellular differentiation. Intracellular copper accumulates in metallothionein in copper overload diseases, such as Wilson s disease, forming two distinct molecular forms one with 12 Cu(I) equivalents bound, in which all 20 thiolate ligands of the protein participate in metal binding the other with eight Cu(I)/ metallothionein a molecules, with between 12-14 cysteines involved in Cu(I) coordination (Pountney et ah, 1994). Although the role of specific metallothionein isoforms in zinc homeostasis and apoptosis is established, its primary function in copper metabolism remains enigmatic (Vasak and Hasler, 2000). 

Kondo, N., Isobe, M., Imai, K. Goto, T. (1985). Synthesis of metallothionein-like peptides cadystin A and B occurring in a fission yeast, and their isomers. Agricultural and Biological Chemistry 49, 71-83. 

The mechanism by which MTF-1 facilitates zinc-induction of metallothionein promoter through the MREs is not known, but several models have been proposed. First, zinc may act as a coinducer by binding to MTF-1 and creating an allosteric change, allowing MTF-1 to bind to the MREs. The model proposed for mammalian MTF-l/MRE interaction has already been proven for yeast copper metallothionein systems (Furst et al., 1988). Another possibility may be that, under normal conditions, an inhibitor binds MTF-1. When an influx of zinc occurs, MTF-1 binds the zinc, undergoes a conformational change and is released from the inhibitor. The protein would then have the ability to bind to the MREs. Finally, upon an increase in intracellular zinc concentration, a specific coactivator may bind zinc and interact with MTF-1 to maximally induce transcription. 

Fig. 1. Schematic overview of copper trafficking and homeostasis inside the yeast cell. The actions of Mad and Ace 1, copper-dependent metalloregulatory transcription factors, control the production of copper import [copper transporter (Ctr) and reductase (Fre)] and detoxification/sequestration [metallothionein (MT)] machineries, respectively. Three chaperone-mediated delivery pathways are shown. Atxl shuttles Cu(I) to the secretory pathway P-type ATPase Ccc2 (right). CCS delivers Cu(I) to the cytoplasmic enzyme copper-zinc superoxide dismutase (SOD) (left). Coxl7 shuttles Cu(I) to cytochrome c oxidase (CCO) in the mitochondria (bottom). Mitochondrial proteins Scol and Sco2 may also play a role in copper delivery to the CuA and CuB sites of CCO. Copper metabolism and iron metabolism are linked through the actions of Fet3, a copper-containing ferroxidase required to bring iron into the cell (lower right) (see text).

In past years, on line chromatographic coupling techniques such as HPLC and CE coupled to ICP-MS with the isotope dilution technique have been used for element quantification in speciation analysis. An interesting application of the isotope dilution technique in medical research was proposed recently by Prange and co-workers, who added highly enriched " S, Cu, Zn and Cd spikes to the interface of the CE-ICP-MS system. The authors separated isoforms of metallothionein (e.g., of rabbit liver) by capillary electrophoresis and quantified S, Cd, Cu and Zn concentrations in isoforms by ICP-SFMS using the isotope dilution technique. A new selenized yeast reference material (SELM-1) for methionine, selenomethionine (SeMet) and total selenium content has also certified by an intercomparison exercise. ... 

The primary organs for copper storage are the liver and spleen, where the metal is found in the cytosol in superoxide dismutase see Copper Proteins with Type Sites) or metallothionein see Metallothiondns) In response to a copper challenge, yeast adaptively synthesizes metallothionein to detoxify the metal. Copper is also bound, transported, and assimilated into tissues by ceruloplasmin. 

It is suggested that zinc is stored by metallothioneins in many tissues. These are low molecular weight proteins with a high incidence of cysteine residues. A zinc-binding protein, which is similar to metallothionein, has been isolated from yeasts and the cyanobacterium Anacystis nidulansf Zinc uptake in energy-starved Candida utilis requires protein synthesis. While it is possible that... 

In response to heavy metal exposure, certain plants and yeasts produce PCs, analogous to the sulfur-rich protein metallothionein made by vertebrates. PCs are sulfur-rich peptides of the general chemical makeup (y-Glu-Cys) -Gly where = 2 -11 (Fig. 7.7). PCs are... 

Carri MT, Galliazzo F, Ciriolo MR, Rotilio G. Evidence for co-regulation of Cu,Zn superoxide dismutases and metallothionein gene expression in yeast through transcriptional control by copper via the ACE1 factor. FEBS Lett 278 263-266, 1991. 

In mammalians these metallothioneins normally possess chain lengths of 61 amino acids, of which 20 are invariant cysteines residues [58,316], These 20 residues participate in the binding of the up to twelve metal ions. Class II metallothioneins show little or no phylogenetic homology to the metallothioneins of class I, for instance, in sea urchins [317] and yeast [318]. Class III metallothio-... 

Thiolate and related complexes are studied as models for metallothioneins. For example, the Cu(I)-containing metaUothionein in yeast has been modelled by [Cu4(SPh)5] (28.4), while model studies on canine liver cuprothionein have utilized complex 28.5 in which the Cys residues are replaced by thiourea hgands. Among Cd S -containing clusters studied as models for Cd -containing metallothioneins is [Cd3(SC5H2 Pr3)7] (28.6). 

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