Metallothioneins (MTs) were discovered in 1957 and identified as low-molecular weight sulfhydryl-rich proteins. MTs belong to a superfamily of intracellular metal-binding proteins, present in virtually all living organisms, with features common to the archetypal. MT was first isolated from horse kidney and characterized by Margoshes and Vallee [1]. In this work, we wish to briefly summarize the current knowledge regarding the MT forms. All vertebrates examined contain two or more distinct MT isoforms designated MT-1 through MT-4. The three-dimensional structures of MTs from mammalian that have been determined so far show a monomeric protein composed of two globular domains, each encompassing a metal–thiolate cluster. The metallothionein isoform A (MTA) is a 64-residue metalloprotein, which contains essentially the same number of metal-chelating Cys–Cys and Cys–Xxx–Cys motifs (where Xxx stands for any amino acid, other than Cys) and metal ions [2, 3]. These cysteine-rich proteins are localized in cytoplasm and some organelles, predominantly in mitochondria, where their presence is sensitively and strictly regulated by the oxidative state induced by mitochondrial respiration. Depending on the cell state, but especially presence of oxidative stress, MTs are rapidly translocated to the nucleus through nuclear pore complexes. MT localized in the nuclei is oxidized there and it is transported to cytosol; this system is balanced [3].

b Central European Institute of Technology Brno University of Technology

Department of Chemistry and Biochemistry Faculty of Agronomy Mendel University in Brno

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