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Multiple bacteria encode metallothioneinsand SmtA-like zinc fingers

Lookup NU author(s): Andrea Robinson, Peter Bowness, Professor Nigel Robinson


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Zinc is essential but toxic in excess. Bacterial metallothionein,SmtA from Synechococcus PCC 7942, sequesters and detoxifies four zinc ions per molecule and contains a zinc finger structurally similar to eukaryotic GATA. The dearth of other reported bacterial metallothioneins has been surprising. Here we describe related bacterial metallothioneins (BmtA) from Anabaena PCC 7120, Pseudomonas aeruginosa and Pseudomonas putida that bind multiple zinc ions with high stability towards protons. Thiol modification demonstrates that cysteine coordinates zinc in all of these proteins. Additionally, (111) Cd-NMR,and Cd-111-edited H-1-NMR, identified histidine ligands in Anabaena PCC 7120 BmtA, analogous to SmtA. A related Escherichia coli protein bound only a single zinc ion, via four cysteine residues, with low stability towards protons; Cd-111-NMR and (111) Cd-edited H-1-NMR confirmed exclusive cysteine-coordination, and these cysteine residues reacted rapidly with 5,5'-dithiobis-(2-nitrobenzoic acid). H-1-NMR of proteins from P. aeruginosa, Anabaena PCC 7120 and E. coli generated fingerprints diagnostic for the GATA-like zinc finger fold of SmtA. These studies reveal first the existence of multiple bacterial metallothioneins, and second proteins with SmtA-like lone zinc fingers, devoid of a cluster,and designated GatA. We have identified 12 smtA-like genes in sequence databases including four of the gatA type.

Publication metadata

Author(s): Bowness PW; Robinson AK; Robinson NJ; Blindauer CA; Harrison MD; Parkinson JA; Sadler PJ

Publication type: Article

Publication status: Published

Journal: Molecular Microbiology

Year: 2002

Volume: 45

Issue: 5

Pages: 1421-1432

ISSN (print): 0950-382X

ISSN (electronic): 1365-2958

Publisher: Wiley-Blackwell Publishing Ltd.


DOI: 10.1046/j.1365-2958.2002.03109.x


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