Metal binding properties and structure of a type III metallothionein from the metal hyperaccumulator plant Noccaea caerulescens.
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.
Université Libre de Bruxelles, Brussels, Belgium.
Lucia Rubio
LR
Fernandez
Guy
G
Vandenbussche
Nancy
N
Roosens
Cédric
C
Govaerts
Erik
E
Goormaghtigh
Nathalie
N
Verbruggen
D000595:Amino Acid Sequence; D019607:Brassicaceae / Q000378:metabolism*; D002413:Cations, Divalent; D003545:Cysteine / Q000737:chemistry / Q000235:genetics; D008668:Metallothionein / Q000737:chemistry*; D019216:Metals, Heavy / Q000737:chemistry*; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation
D002413:Cations, Divalent; D019216:Metals, Heavy; D010940:Plant Proteins; D008668:Metallothionein; D003545:Cysteine