title: Sunflower metallothionein family characterisation. Study of the Zn(II)- and Cd(II)-binding abilities of the HaMT1 and HaMT2 isoforms.
abstract: Plant metallothioneins (MTs) constitute a family of small Cys-rich proteins capable of coordinating metal ions, significantly differing from microbial and animal MTs. They are divided into four subfamilies depending on the Cys pattern in their sequence. In this work, the MT system of the sunflower plant (Helianthus annuus) has been defined, with ten genes coding for MTs (HaMT) belonging to the four plant MT subfamilies; three HaMT1, four HaMT2, one HaMT3 and two HaMT4 isoforms. The gene expression pattern and capacity to confer metal resistance to yeast cells have been analysed for at least one member of each subfamily. The divalent metal ion-binding abilities of HaMT1-2 and HaMT2-1 (the isoforms encoded by the most abundantly expressed HaMT1 and HaMT2 isogenes) have been characterised, as HaMT3 and HaMT4 were previously studied. Those isoforms constitute an optimum material to study the effect of Cys number variability on their coordination abilities, as they exhibit additional Cys residues regarding the canonical Cys pattern of each subfamily. Our results show that the variation in the number of Cys does not drastically modify their M(II)-binding abilities, but instead modulates the degree of heterogeneity of the corresponding recombinant syntheses. Significantly, the Zn(II)-HaMT1 complexes were highly susceptible to proteolytic cleavage. The recombinant Cd-MT preparations of both isoforms exhibit significant acid-labile sulphide content-Cd6S8 or Cd7S7 species. Overall results suggest that HaMT2-1 is probably associated with Cd(II) detoxification, in contrast to HaMT1-2, which may be more related to physiological functions, such as metal ion transport and delivery.
authors.affiliation: Departament de Química, Facultat de Ciències, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Barcelona, Spain; Departament de Genètica, Facultat de Biologia, Universitat de Barcelona, Av. Diagonal 645, 08028 Barcelona, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Tomas
authors.affiliation: Centro de Estudios Fotosintéticos y Bioquímicos, CONICET, Suipacha 531, 2000 Rosario, Argentina.
authors.forename: M A
authors.initials: MA
authors.lastname: Pagani
authors.affiliation: Centro de Estudios Fotosintéticos y Bioquímicos, CONICET, Suipacha 531, 2000 Rosario, Argentina.
authors.forename: C S
authors.initials: CS
authors.lastname: Andreo
authors.affiliation: Departament de Química, Facultat de Ciències, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Barcelona, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Capdevila
authors.affiliation: Departament de Genètica, Facultat de Biologia, Universitat de Barcelona, Av. Diagonal 645, 08028 Barcelona, Spain.
authors.forename: S
authors.initials: S
authors.lastname: Atrian
authors.affiliation: Departament de Química, Facultat de Ciències, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Barcelona, Spain. Electronic address: Roger.Bofill@uab.cat.
authors.forename: R
authors.initials: R
authors.lastname: Bofill
mesh_terms: D000595:Amino Acid Sequence; D002104:Cadmium / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D002942:Circular Dichroism; D004351:Drug Resistance / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D005816:Genetic Complementation Test; D006368:Helianthus / Q000235:genetics / Q000378:metabolism*; D008668:Metallothionein / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000235:genetics / Q000254:growth & development; D017386:Sequence Homology, Amino Acid; D021241:Spectrometry, Mass, Electrospray Ionization; D013056:Spectrophotometry, Ultraviolet; D015032:Zinc / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D010940:Plant Proteins; D020033:Protein Isoforms; D011994:Recombinant Proteins; D002104:Cadmium; D008668:Metallothionein; D015032:Zinc
keywords: Biological function; Cd-binding; Metallothionein; Plant MT; Sunflower; Zn-binding