ISBN: 978-83-60043-10-3 - eurobic9

Eurobic9, 2-6 September, 2008, Wrocław, Poland
P149. Approach to the Metal Specificity of the Terrestrial Snail
Metallothionein Isoforms through the Analysis of Their Recombinant
Complexes
O. Palacios a , A. Pagani b , M. Egg c , M. Hockner c , R. Dallinger c , M. Capdevila a ,
S. Atrian b
a Química, Universitat Autònoma de Barcelona, Campus de Bellaterra, 08193, Cerdanyola del Vallés, Spain,
b Genètica, Universitat de Barcelona, Av. Diagonal, 08028, Barcelona, Spain
c Zoology and Limnology, University of Innsbruck, , 6020, Innsbruck, Austria
e-mail: oscar.palacios@uab.cat
Many organisms contain several metallothionein (MT) isoforms able to play different physiologic roles. A clear
example is found in the snail H.pomatia [1], harboring two MT isoforms. The HpCdMT gene is induced by Cd 2+
and expressed in the midgut gland. HpCuMT is expressed constitutively only in the rogocites, yielding
homometallic Cu + complexes, so that a role in Cu homeostasis is hypothesized. In other invertebrates, such as
D.melanogaster, the existence of several MT isoforms, all of them with similar metal binding preferences, is
known [2]. In order to shed light on the metal binding behavior of the two H.pomatia MTs, HpCuMT and
HpCdMT, they were recombinantly produced in E.coli cultures supplemented with either Zn 2+ , Cd 2+ or Cu 2+
ions. The metal-MT complexes obtained in vivo from the recombinant bacteria, as well as those obtained in vitro
after Zn/M (M= Cd or Cu) replacement, were analysed by ICP-AES, UV and CD spectroscopy and ESI-TOF
MS.Our results confirm the high specificity of HpCuMT for copper, since it is able to fold into single Cu12-MT
species under low O2 conditions, unlike the HpCdMT isoform. Also, the high specificity of the HpCdMT
isoform for divalent metal ions (Zn 2+ and Cd 2+ ) is highlighted, as it yields Zn6- and Cd6-MT species,
respectively. These data are in perfect concordance with those available about the metal specificity of both native
isoforms, and thus their specific functions, an scenario that has so far not been described for other organisms.
References:
[1] R. Dallinger, B. Berger, P.E. Hunziker, J.H.R. Kägi, Nature, 1997, 388, 237-238
[2] D. Egli, J. Domenech, A. Selvaraj, K. Balamurugan, H. Hua, M. Capdevila, O. Georgiev, W. Schaffner, S.
Atrian, Genes to Cells, 2006, 11, 647-658
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