Metal binding properties and structure of a type III metallothionein from the metal hyperaccumulator plant Noccaea caerulescens |
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Authors: | Fernandez Lucia Rubio Vandenbussche Guy Roosens Nancy Govaerts Cédric Goormaghtigh Erik Verbruggen Nathalie |
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Affiliation: | Laboratoire de Physiologie et de Génétique Moléculaire des Plantes, Université Libre de Bruxelles (ULB), B-1050 Brussels, Belgium. |
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Abstract: | Metallothioneins (MT) are low molecular weight proteins with cysteine-rich sequences that bind heavy metals with remarkably high affinities. Plant MTs differ from animal ones by a peculiar amino acid sequence organization consisting of two short Cys-rich terminal domains (containing from 4 to 8 Cys each) linked by a Cys free region of about 30 residues. In contrast with the current knowledge on the 3D structure of animal MTs, there is a striking lack of structural data on plant MTs. We have expressed and purified a type III MT from Noccaea caerulescens (previously Thlaspi caerulescens). This protein is able to bind a variety of cations including Cd(2+), Cu(2+), Zn(2+) and Pb(2+), with different stoichiometries as shown by mass spectrometry. The protein displays a complete absence of periodic secondary structures as measured by far-UV circular dichroism, infrared spectroscopy and hydrogen/deuterium exchange kinetics. When attached onto a BIA-ATR biosensor, no significant structural change was observed upon removing the metal ions. |
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