 visitant ::
identificació
|
|||||||||||||||
|
Cerca | Lliura | Ajuda | Servei de Biblioteques | Sobre el DDD | Català English Español | |||||||||
| Pàgina inicial > Articles > Articles publicats > Hints for metal-preference protein sequence determinants : |
(Universitat Autònoma de Barcelona. Departament de Química) (Universitat Autònoma de Barcelona. Departament de Química) (Universitat Autònoma de Barcelona. Departament de Química)| Data: | 2015 |
| Resum: | The metal binding preference of metallothioneins (MTs) groups them in two extreme subsets, the Zn/Cd- and the Cu-thioneins. Ciliates harbor the largest MT gene/protein family reported so far, including 5 paralogs that exhibit relatively low sequence similarity, excepting MTT2 and MTT4. In Tetrahymena thermophila, three MTs (MTT1, MTT3 and MTT5) were considered Cd-thioneins and two (MTT2 and MTT4) Cu-thioneins, according to gene expression inducibility and phylogenetic analysis. In this study, the metal-binding abilities of the five MTT proteins were characterized, to obtain information about the folding and stability of their cognate- and non-cognate metal complexes, and to characterize the T. thermophila MT system at protein level. Hence, the five MTTs were recombinantly synthesized as Zn²⁺ -, Cd²⁺ - or Cu⁺ -complexes, which were analyzed by electrospray mass spectrometry (ESI-MS), circular dichroism (CD), and UV-vis spectrophotometry. Among the Cd-thioneins, MTT1 and MTT5 were optimal for Cd²⁺ coordination, yielding unique Cd₁₇ and Cd₈ complexes, respectively and Cd- complexes, respectively. When binding Zn²⁺, they rendered a mixture of Zn-species. Only MTT5 was capable to coordinate Cu⁺, although yielding heteronuclear Zn-, Cu-species or highly unstable Cu-homometallic species. MTT3 exhibited poor binding abilities both for Cd²⁺ and for Cu⁺, and although not optimally, it yielded the best result when coordinating Zn²⁺. The two Cu-thioneins, MTT2 and MTT4 isoforms formed homometallic Cu-complexes (major Cu-MTT) upon synthesis in Cu-supplemented hosts. Contrarily, they were unable to fold into stable Cd-complexes, while Zn-MTT species were only recovered for MTT4 (major Zn-MTT4). Thus, the metal binding preferences of the five T. thermophila MTs correlate well with their previous classification as Cd- and Cu-thioneins, and globally, they can be classified from Zn/Cd- to Cu-thioneins according to the gradation: MTT1>MTT5>MTT3>MTT4>MTT2. The main mechanisms underlying the evolution and specialization of the MTT metal binding preferences may have been internal tandem duplications, presence of doublet and triplet Cys patterns in Zn/Cd-thioneins, and optimization of site specific amino acid determinants (Lys for Zn/Cd- and Asn for Cu-coordination). |
| Ajuts: | Ministerio de Economía y Competitividad BIO2012-39682-C02-01 Ministerio de Economía y Competitividad BES-2010-036553) Ministerio de Economía y Competitividad CGL2008-00317/BOS Agència de Gestió d'Ajuts Universitaris i de Recerca 2014/SGR-423 |
| Drets: | Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, la comunicació pública de l'obra i la creació d'obres derivades, sempre que no sigui amb finalitats comercials, i sempre que es reconegui l'autoria de l'obra original.  |
| Llengua: | Anglès |
| Document: | Article ; recerca ; Versió publicada |
| Matèria: | Metallothionein ; Functional differentiation ; Metal specificity ; Zinc ; Copper ; Tetrahymena thermophila |
| Publicat a: | International journal of biological sciences, Vol. 11 (March 2015) , p. 456-471, ISSN 1449-2288 |
