Pb(ii) binding to the brain specific mammalian metallothionein isoform MT3 and its isolated αMT3 and βMT3 domains.

The toxicity of lead, one of the most ubiquitous toxic metals, is well known. Some of its pathological effects are related to its preference for the sulfhydryl groups of proteins. Metallothioneins (MT) are a particular family of metalloproteins characterized by their high Cys content that, among other functions, are linked to the detoxification of heavy metals.

A study of the Pb(II) binding to recombinant mouse Zn(7)-metallothionein 1 and its domains by ESI TOF MS.

This work reports, for the first time, a complete analysis of the binding of Pb(II) ions to mammalian Zn-metallothionein (MT) and its individual domains (alpha and beta) by means of ESI TOF MS. The use of highly pure recombinant Zn-MT and high resolution MS allowed the identification of the different heteronuclear Pb,Zn-MT and homonuclear Pb-MT complexes formed by Zn/Pb replacement in the initial Zn-MT complexes at pH 7. The results obtained showed, both for the whole Zn(7)-MT and for its individual Zn(4)-alpha and Zn(3)-beta fragments, a partial substitution of the Zn initially bound to give rise to the formation of both Pb,Zn-MT and Pb-MT species.

Effects of short-term exposure to the DDT metabolite p,p'-DDE on bone tissue in male common frog (Rana temporaria).

Experimental studies as well as studies in free-ranging animals have shown that endocrine-disrupting chemicals (EDCs) impair bone tissue composition and strength. The aim of the present study was to expand our studies on bone tissue in a new group of animals by investigating whether bone tissue in frogs is an additional potential target of EDCs. Adult male European common frogs (Rana temporaria) were divided into 5 groups (n = 20) and injected (sc, single injection) with p,p'-DDE, a total dose of 0.

Effects of p,p'-DDE on retinoid homeostasis and sex hormones of adult male European common frogs (Rana temporaria).

Reports of declining numbers of species and individuals of amphibians in most parts of the world have caused great concern. Several causative factors have been linked to this amphibian decline, and increased environmental pollution related to pesticide use seems to be one important factor. Persistent organic pollutants may act as endocrine disrupters, and thereby exert adverse effects on development (metamorphosis, growth and sexual differentiation) in amphibians.

Altered hepatic retinol and CYP26 levels in adult European common frogs (Rana temporaria) exposed to p,p'-DDE.

The effects of environmental contamination on amphibians are of particular concern because there are reports of declining numbers of species and individuals in most parts of the world during the last 50 years. During the last decade there has been increased focus on the role of persistent organic pollutants as retinoid (vitamin A) disrupters, and their effects on development, growth and sexual differentiation. To study the effects of p,p'-DDE, one of the most persistent metabolites of the pesticide DDT, on retinol homeostasis, we subcutaneously exposed adult male European common frogs (Rana temporaria) to different doses of p,p'-DDE (0, 0.

Mercury(II) binding to metallothioneins. Variables governing the formation and structural features of the mammalian Hg-MT species.

With the aim of extending our knowledge on the reaction pathways of Zn-metallothionein (MT) and apo-MT species in the presence of Hg(II), we monitored the titration of Zn7-MT, Zn4-alphaMT and Zn3-betaMT proteins, at pH 7 and 3, with either HgCl2 or Hg(ClO4)2 by CD and UV-vis spectroscopy. Detailed analysis of the optical data revealed that standard variables, such as the pH of the solution, the binding ability of the counter-ion (chloride or perchlorate), and the time elapsed between subsequent additions of Hg(II) to the protein, play a determinant role in the stoichiometry, stereochemistry and degree of folding of the Hg-MT species. Despite the fact that the effect of these variables is unquestionable, it is difficult to generalize.

Chemical foundation of the attenuation of methylmercury(II) cytotoxicity by metallothioneins.

To elucidate the chemical interactions underlying the role of metallothioneins (MTs) in reducing the cytotoxicity caused by MeHg(II), we monitored in parallel by electronic absorption and CD spectroscopies the stepwise addition of MeHgCl stock solution to mammalian Zn(7)-MT1 and the isolated Zn(4)-alphaMT1 and Zn(3)-betaMT1 fragments. The incorporation of MeHg(+) into Zn(7)-MT and Zn(3)-betaMT entails total displacement of Zn(II) and unfolding of the protein. However, both features are only partial for Zn(4)-alphaMT.