title: Does Variation of the Inter-Domain Linker Sequence Modulate the Metal Binding Behaviour of Helix pomatia Cd-Metallothionein?
abstract: Snail metallothioneins (MTs) constitute an ideal model to study structure/function relationships in these metal-binding polypeptides. Helix pomatia harbours three MT isoforms: the highly specific CdMT and CuMT, and an unspecific Cd/CuMT, which represent paralogous proteins with extremely different metal binding preferences while sharing high sequence similarity. Preceding work allowed assessing that, although, the Cys residues are responsible for metal ion coordination, metal specificity or preference is achieved by diversification of the amino acids interspersed between them. The metal-specific MT polypeptides fold into unique, energetically-optimized complexes of defined metal content, when binding their cognate metal ions, while they produce a mixture of complexes, none of them representing a clear energy minimum, with non-cognate metal ions. Another critical, and so far mostly unexplored, region is the stretch linking the individual MT domains, each of which represents an independent metal cluster. In this work, we have designed and analyzed two HpCdMT constructs with substituted linker segments, and determined their coordination behavior when exposed to both cognate and non-cognate metal ions. Results unequivocally show that neither length nor composition of the inter-domain linker alter the features of the Zn(II)- and Cd(II)-complexes, but surprisingly that they influence their ability to bind Cu(I), the non-cognate metal ion.
authors.affiliation: Departament de Química, Facultat de Ciències, Universitat Autònoma de Barcelona, E-08193 Cerdanyola del Vallès, Spain. selenebdn89@gmail.com.
authors.forename: Selene
authors.initials: S
authors.lastname: Gil-Moreno
authors.affiliation: Departament de Genètica, Facultat de Biologia, Universitat de Barcelona, Av. Diagonal 643, E-08028 Barcelona, Spain. ejimenezmarti@gmail.com.
authors.forename: Elena
authors.initials: E
authors.lastname: Jiménez-Martí
authors.affiliation: Departament de Química, Facultat de Ciències, Universitat Autònoma de Barcelona, E-08193 Cerdanyola del Vallès, Spain. oscar.palacios@uab.cat.
authors.forename: Òscar
authors.initials: Ò
authors.lastname: Palacios
authors.affiliation: Institute of Organic Chemistry, University of Zurich, 8057 Zurich, Switzerland. zerbe@oci.uzh.ch.
authors.forename: Oliver
authors.initials: O
authors.lastname: Zerbe
authors.affiliation: Institute of Zoology, University of Innsbruck, Technikerstraße 25, A-6020 Innsbruck, Austria. reinhard.dallinger@uibk.ac.at.
authors.forename: Reinhard
authors.initials: R
authors.lastname: Dallinger
authors.affiliation: Departament de Química, Facultat de Ciències, Universitat Autònoma de Barcelona, E-08193 Cerdanyola del Vallès, Spain. merce.capdevila@uab.cat.
authors.forename: Mercè
authors.initials: M
authors.lastname: Capdevila
authors.affiliation: Departament de Genètica, Facultat de Biologia, Universitat de Barcelona, Av. Diagonal 643, E-08028 Barcelona, Spain. satrian@ub.edu.
authors.forename: Sílvia
authors.initials: S
authors.lastname: Atrian
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002104:Cadmium / Q000378:metabolism*; D017124:Conserved Sequence; D006372:Helix, Snails / Q000235:genetics / Q000378:metabolism; D008668:Metallothionein / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D011110:Polymorphism, Genetic; D011485:Protein Binding; D015032:Zinc / Q000378:metabolism
chemical_list: D002104:Cadmium; D008668:Metallothionein; D015032:Zinc
keywords: Cd-isoform; Helix pomatia; domain linker sequence; metal binding; metallothionein