Mercury(II) binding to metallothioneins. Variables governing the formation and structural features of the mammalian Hg-MT species.
With the aim of extending our knowledge on the reaction pathways of Zn-metallothionein (MT) and apo-MT species in the presence of Hg(II), we monitored the titration of Zn7-MT, Zn4-alphaMT and Zn3-betaMT proteins, at pH 7 and 3, with either HgCl2 or Hg(ClO4)2 by CD and UV-vis spectroscopy. Detailed analysis of the optical data revealed that standard variables, such as the pH of the solution, the binding ability of the counter-ion (chloride or perchlorate), and the time elapsed between subsequent additions of Hg(II) to the protein, play a determinant role in the stoichiometry, stereochemistry and degree of folding of the Hg-MT species. Despite the fact that the effect of these variables is unquestionable, it is difficult to generalize. Overall, it can be concluded that the reaction conditions [pH, time elapsed between subsequent additions of Hg(II) to the protein] affect the structural properties more substantially than the stoichiometry of the Hg-MT species, and that the role of the counter-ion becomes particularly apparent on the structure of overloaded Hg-MT.
Leiva-Presa
Angels
A
Departament de Química, Facultat de Ciències, Universitat Autònoma de Barcelona, Spain.
Capdevila
Mercè
M
Gonzàlez-Duarte
Pilar
P
D000818:Animals; D002942:Circular Dichroism; D008628:Mercury / Q000378:metabolism*; D008668:Metallothionein / Q000378:metabolism*; D051379:Mice; D015394:Molecular Structure; D011485:Protein Binding; D011994:Recombinant Proteins / Q000378:metabolism; D013056:Spectrophotometry, Ultraviolet
D011994:Recombinant Proteins; D008668:Metallothionein; D008628:Mercury