Metallothionein protein evolution: a miniassay

Abstract

Metallothionein (MT) evolution is one of the most obscure yet fascinating aspects of the study of these atypical metal-binding peptides. The different members of the extremely heterogeneous MT protein superfamily probably evolved through a web of duplication, functional differentiation, and/or convergence events leading to the current scenario, which is particularly hard to interpret in terms of molecular evolution. Difficulties in drawing straight evolutionary relationships are reflected in the lack of definite MT classification criteria. Presently, MTs are categorized either according to a pure taxonomic clustering or depending on their metal binding preferences and specificities. Extremely well documented MT revisions were recently published. But beyond classic approaches, this review of MT protein evolution will bring together new aspects that have seldom been discussed before. Hence, the emergence of life on our planet, since metal ion utilization is accepted to be at the root of the emergence of living organisms, and global trends that underlie structural and functional MT diversification, will be presented. Major efforts are currently being devoted to identifying rules for function-constrained MT evolution that may be applied to different groups of organisms.

Cantareus aspersus metallothionein metal binding abilities: The unspecific CaCd/CuMT isoform provides hints about the metal preference determinants in metallothioneins

“…Cd 2+ , Pb 2+ or Hg 2+ ) appear as the most relevant [1,2]. MTs constitute a polymorphic system in practically all the organisms, so that the diversification of isoforms along the branches of the tree of life may underlie their ability to adapt and be useful for a great diversity of metal-related molecular functions [3,4]. MT isoforms are generally homologous proteins that exhibit either similar or highly different preferences for divalent (Zn 2+ and Cd 2+ ) vs. monovalent (Cu + ) metal ion coordination [2,5].…”

Tissue-specificity and phylogenetics of Pl-MT mRNA during Paracentrotus lividus embryogenesis

“…MTs are ubiquitous proteins present in many organisms, ranging from plants to humans (Capdevila and Atrian, 2011). Due to the extreme heterogeneity among MTs, a complex classification of these proteins has been developed by Binz and Kagi (1999), who grouped all aminoacidic MT sequences into 15 families and a number of subfamilies, subgroups and isoforms, on the basis of phylogenetically related and alignable sequences.…”

PIXE-electrophoresis shows starving collembolan reallocates protein-bound metals

“…The traces of metal above the background level found in those specimens were bound to proteins larger than 20 kDa, that is, larger than proteins normally defined as metallothioneins (Kägi 1991;Capdevila and Atrian 2011). As the same size distribution of proteins was induced in specimens fed with metals, they seem to play a role in metal detoxification in feeding specimens.…”