Molecular characterization and function analysis of MT-10 and MT-20 metallothionein isoforms from Mytilus galloprovincialis |
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Authors: | Vergani Laura Grattarola Myriam Grasselli Elena Dondero Francesco Viarengo Aldo |
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Affiliation: | Department of Biology, University of Genova, Genova, Corso Europa 26, 16132 Genova, Italy. Laura.Vergani@unige.it |
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Abstract: | Structure and function of molluscan metallothioneins (MTs) are still poorly understood. The sea mussel Mytilus galloprovincialis displays two MT isoforms which differ in both primary sequences and physiological functions. MT-10 is the constitutive isoform, whereas MT-20 is mainly induced by cadmium (Cd). Both MTs were produced as recombinant proteins and showed identical Cd content and similar Cd-binding properties. Conversely, circular dichroism disclosed marked differences in the secondary conformations of the two Cd(7)-MTs. The possible relapses of these structural differences on protein stability and function were assessed. MT-10 presented a higher thermal stability and a more compact structure than MT-20, as it was inferred by absorption and emission spectroscopy studies. Moreover, the kinetics of Cd-release clearly indicated that MT-10 is much more sensitive to oxidation than is MT-20. The observed differences between MT-10 and MT-20 are discussed in terms of the different physiological roles exerted by the two isoforms in mussel. |
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Keywords: | Metallothionein Cadmium-binding Cadmium-release Copper-binding Structure-function relationship Circular dichroism Absorption spectroscopy Fluorescence emission spectroscopy Mytilus galloprovincialis |
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