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3

Bacterial Metallothioneins

The bacterial metallothioneins (MT), BmtAs, constitute a well defined sub-family, sharing a number of characteristics with eukaryotic metallothioneins. They are small, cysteine-rich proteins, are inducible by metal ion stress, and contain metal-thiolate clusters with topologies similar to those of mammalian MTs. They also have a number of features that set them apart from most previously characterized metallothioneins. Most importantly, they adopt a zinc finger-like protein fold, and they contain conserved aromatic residues including histidines. The latter have been shown to modulate thermodynamics and kinetics of metal binding in various ways. The two metal-coordinating His residues in Synechococcus PCC 7942 SmtA enhance the stability of the zinc-thiolate cluster, compared to an all-Cys cluster generated by site-directed mutagenesis. His40 confers structural order to the entire C-terminus, whilst His49 has been shown to play a pivotal role in regulating zinc transfer reactions. The sequences of SmtA orthologues from other species show varations in the loop containing this residue, and preliminary studies have shown that this crucially affects metal binding properties of the proteins.

Publication details


Print publication date
19 Jan 2009
Copyright year
2009
Print ISBN
978-1-84755-899-2
PDF eISBN
978-1-84755-953-1
From the book series:
Metal Ions in Life Sciences