Tunicates Illuminate the Enigmatic Evolution of Chordate Metallothioneins by Gene Gains and Losses, Independent Modular Expansions, and Functional Convergences.

Sara Calatayud, Mario Garcia-Risco, Òscar Palacios, Mercè Capdevila, Cristian Cañestro, Ricard Albalat

Molecular biology and evolution 2021 Sep 27

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To investigate novel patterns and processes of protein evolution, we have focused in the metallothioneins (MTs), a singular group of metal-binding, cysteine-rich proteins that, due to their high degree of sequence diversity, still represents a "black hole" in Evolutionary Biology. We have identified and analyzed more than 160 new MTs in nonvertebrate chordates (especially in 37 species of ascidians, 4 thaliaceans, and 3 appendicularians) showing that prototypic tunicate MTs are mono-modular proteins with a pervasive preference for cadmium ions, whereas vertebrate and cephalochordate MTs are bimodular proteins with diverse metal preferences. These structural and functional differences imply a complex evolutionary history of chordate MTs-including de novo emergence of genes and domains, processes of convergent evolution, events of gene gains and losses, and recurrent amplifications of functional domains-that would stand for an unprecedented case in the field of protein evolution. © The Author(s) 2021. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

Citation

Sara Calatayud, Mario Garcia-Risco, Òscar Palacios, Mercè Capdevila, Cristian Cañestro, Ricard Albalat. Tunicates Illuminate the Enigmatic Evolution of Chordate Metallothioneins by Gene Gains and Losses, Independent Modular Expansions, and Functional Convergences. Molecular biology and evolution. 2021 Sep 27;38(10):4435-4448