Heavy-metal detoxification capacity of different soybean metallothioneins

TOMAS M; CARRILLO J; ANDREO CS; CAPDEVILA M; PAGANI MA; ATRIAN S; BOFILL R

Barcelona

Simposio; 11th International Symposium on Applied Bioinorganic Chemistry; 2011

Soybean (Glycine max) represents the legume crop with the highest agroeconomical importance in Argentina. Therefore, the analysis of the molecular determinants of its heavy metal resistance capacity becomes of utmost interest. Among those, metallothioneins (MTs) -low molecular weight, Cys-rich proteins with high heavy metal binding capacity- become of special interest. Here, we perform a comparative analysis of the metal binding abilities of four G. max MT isoforms –each of them belonging to one of the four plant MT types[1]– obtained through recombinant synthesis in Zn(II)-, Cd(II)- or Cu(II)-supplemented cultures of E. coli. Metal-MT stoichiometries for the M(II)-GmMT1, M(II)-GmMT2 and M(II)-GmMT3 complexes (M = Zn or Cd) match well with those described in the literature for MTs from other vegetal species of the same type,[2] and GmMT4 generates a mixture of Zn5- and Zn6-GmMT4. When comparing these results with those from the wheat Ec-1 protein,[3] the best known type 4 plant MT that generates unique Zn6-Ec-1 complexes, it is clear that GmMT4 possesses a lower Zn(II) binding capacity, probably because of the absence of one His residue in relation to Ec-1. On the other hand, preliminary results with the Cu(I)-GmMT complexes show a higher Cu(I) preference for isoforms 1 and 3 with respect to isoforms 2 and 4