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].

• MeSH
• kovy MeSH
• lidé MeSH
• metalothionein * analýza   fyziologie   chemie   MeSH
• nádorové biomarkery * analýza   metabolismus   MeSH
• nádory diagnóza   metabolismus   MeSH
• protein - isoformy MeSH
• spektrometrie hmotnostní - ionizace laserem za účasti matrice * MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• práce podpořená grantem MeSH
• přehledy MeSH

Increasing emissions of heavy metals such as cadmium, mercury, and arsenic into the environment pose an acute problem for all organisms. As a mass of protection, many of them, develop mechanisms of full resistance or at least exhibit partially resisting toward these effects. In this way, based on the chemical similarity of the involved metallic species, they are able, to replace them with viable metals necessary for the effective functioning of the cell. These heavy metals may be bound to the functional groups of proteins and modify their structure and through this also affect their physiological function 1, 2. Higher plants, algae, certain yeasts and animals are able to respond to heavy metals by synthesizing phytochelatins (PCs) and related cysteine-rich polypeptides. Phytochelatin synthases are γ-glutamylcysteine (γ-Glu-Cys) dipeptidyl transpeptidases that catalyze the synthesis of heavy metal-binding PCs 3, 4. PCs, cysteine-rich peptides, are produced from glutamine, cysteine and glycine. Unlike commonmetal-binding structures, MT and GSH, PCs are not gene-encoded, but enzymatically synthesized peptides 5. PCs have been identified in a wide variety of plant species, microorganisms and some invertebrates 6-10. They are structurally related to glutathione (GSH) and were presumed to be the products of a biosynthetic pathway. Numerous physiological, biochemical and genetic studies have confirmed GSH as the substrate for PCs biosynthesis 11, 12. The general structure of PCs is (c-Glu-Cys)n-Gly, with increasing repetitions of the dipeptide Glu-Cys linked through a c-carboxylamide bond (Fig 1), where n varies from 2 to 11, but typically reaching not further than five 13. Except glycine, also other amino acid residues can be found on C-terminal end of (γ-Glu-Cys)n peptides. Examples of which, like Ser, Glu, Gln and Ala are often found at this position in some plant species, and they are assumed to be functionally analogous and synthesised via essentially similar biochemical pathways 14, 15. In in vitro studies of PC synthase expressed in E. coli or in S. cerevisiae, the enzyme was activated to varying extents by Cd, Cu, Ag, Hg, Zn and Pb ions 16-18. PC synthase genes were also isolated in A.thaliana 16 and T.aestivum 18. Genes homologous to those from A.thaliana and T.aestivum were also found in S.pombe and C.elegans, suggesting the existence of PC synthase genes in more species 19.

• MeSH
• chemické techniky analytické metody   MeSH
• fytochelatiny * biosyntéza   chemie   metabolismus   MeSH
• rostliny metabolismus   MeSH
• těžké kovy * metabolismus   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• práce podpořená grantem MeSH
• přehledy MeSH

Homeostatic mechanisms preventing the toxicity of free Zn ions in cells involve, among others, cytosolic Zn-binding ligands, particularly the cysteine-rich metallothioneins (MTs). Here we examined the Zn-binding peptides of Russula atropurpurea, an ectomycorrhizal fungus known for its ability to accumulate high amounts of Zn in its sporocarps. The Zn complexes and their peptide ligands were characterized using chromatography, electrophoresis after fluorescent labeling of cysteine residues, and tandem mass spectrometry. Functional complementation assays in Saccharomyces cerevisiae were used to obtain and characterize cDNA sequences. Zn-speciation analysis showed that nearly 80% of the Zn extracted from the sporocarps was associated with cysteine-containing peptides in a 5 kDa complex. Screening of an R. atropurpurea cDNA library for sequences encoding peptides capable of sequestering divalent heavy metals was conducted in the Cd-hypersensitive ycf1Δ yeast. This allowed identification of two cDNAs, RaZBP1 and RaZBP2, which protected the metal-sensitive yeast mutants against Cd and Zn, but not Co, Mn or Cu, toxicity. The corresponding RaZBP1 and RaZBP2 peptides consisting of 53 amino acid (AA) residues and sharing 77% identity showed only a limited sequence similarity to known MTs, particularly due to the absence of multiple Cys-AA-Cys motifs. Both RaZBPs were detected in a native Zn-complex of R. atropurpurea and the recombinant RaZBP1 was found associated with Zn and Cd in yeasts. Altogether, the results point to an important role of RaZBPs in the handling of a substantial portion of the Zn pool in R. atropurpurea.

• MeSH
• Basidiomycota metabolismus   MeSH
• intracelulární prostor metabolismus   MeSH
• kadmium metabolismus   MeSH
• metalothionein chemie   izolace a purifikace   metabolismus   MeSH
• molekulární sekvence - údaje MeSH
• mutace genetika   MeSH
• mykorhiza metabolismus   MeSH
• peptidy chemie   izolace a purifikace   metabolismus   MeSH
• Saccharomyces cerevisiae metabolismus   MeSH
• sekvence aminokyselin MeSH
• sekvenční analýza proteinů MeSH
• sekvenční seřazení MeSH
• zinek chemie   metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH