title: Cantareus aspersus metallothionein metal binding abilities: the unspecific CaCd/CuMT isoform provides hints about the metal preference determinants in metallothioneins.
abstract: In Proteomics, gene/protein families including both specialized and non-specialized paralogs are an invaluable tool to study the evolution of structure/function relationships in proteins. Metallothioneins (MTs) of the pulmonate gastropod molluscs (snails) offer one of the best materials to study the metal-binding specificity of proteins, because they consist of a polymorphic system that includes members with extremely distinct metal preferences but with a high protein sequence similarity. Cantareus aspersus was the first snail where three paralogous MTs were isolated: the highly specific cadmium (CaCdMT) and copper (CaCuMT) isoforms, and an unspecific CaCd/CuMT isoform, so called because it was natively isolated as a mixed Cd and Cu complex. In this work, we have thoroughly analyzed the Zn(2+)-, Cd(2+)- and Cu(+)-binding abilities of these three CaMTs by means of the spectroscopic and spectrometric characterization of the respective recombinant, as well as in vitro-substituted, metal-complexes. The comparison with the orthologous HpMTs and the study of the isoform-determinant residues allow correlating the protein sequence variability with the coordination capabilities of these MTs. Surprisingly, the CaCuMT isoform exhibits a stronger Cu-thionein character than the HpCuMT ortholog, and the CaCd/CuMT isoform could be defined as a non-optimized Cu-thionein, which has not attained any defined functional differentiation in the framework of the snail MT gene/protein family.
authors: Departament de Química, Facultat de Ciències, Universitat Autònoma de Barcelona, E-08193 Cerdanyola del Vallès, Barcelona, Spain.
authors: Sílvia
authors: S
authors: Pérez-Rafael
authors: Departament de Genètica, Facultat de Biologia, Universitat de Barcelona, Av. Diagonal 643, E-08028 Barcelona, Spain.
authors: Freddy
authors: F
authors: Monteiro
authors: Institute of Zoology, University of Innsbruck, Technikerstraße 25, A-6020 Innsbruck, Austria.
authors: Reinhard
authors: R
authors: Dallinger
authors: Departament de Genètica, Facultat de Biologia, Universitat de Barcelona, Av. Diagonal 643, E-08028 Barcelona, Spain.
authors: Sílvia
authors: S
authors: Atrian
authors: Departament de Química, Facultat de Ciències, Universitat Autònoma de Barcelona, E-08193 Cerdanyola del Vallès, Barcelona, Spain. Electronic address: oscar.palacios@uab.cat.
authors: Oscar
authors: O
authors: Palacios
authors: Departament de Química, Facultat de Ciències, Universitat Autònoma de Barcelona, E-08193 Cerdanyola del Vallès, Barcelona, Spain.
authors: Mercè
authors: M
authors: Capdevila
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002104:Cadmium / Q000737:chemistry*; D002413:Cations, Divalent; D002414:Cations, Monovalent; D002942:Circular Dichroism; D003300:Copper / Q000737:chemistry*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D006372:Helix, Snails / Q000737:chemistry* / Q000378:metabolism; D008024:Ligands; D008668:Metallothionein / Q000737:chemistry* / Q000378:metabolism; D008969:Molecular Sequence Data; D011485:Protein Binding; D020033:Protein Isoforms / Q000737:chemistry / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D021241:Spectrometry, Mass, Electrospray Ionization; D015032:Zinc / Q000737:chemistry
chemical_list: D002413:Cations, Divalent; D002414:Cations, Monovalent; D008024:Ligands; D020033:Protein Isoforms; D002104:Cadmium; D003300:Copper; D008668:Metallothionein; D015032:Zinc
keywords: Cadmium; Cantareus aspersus metallothionein; Copper; Sequence determinant