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Mol Microbiol. 2016 Sep;101(5):731-42. doi: 10.1111/mmi.13399. Epub 2016 May 7.

SilE is an intrinsically disordered periplasmic "molecular sponge" involved in bacterial silver resistance.

Author information

1
School of Biosciences, University of Nottingham, Sutton, Bonington, LE12 5RD, United Kingdom.
2
Centre for Biomolecular Sciences, School of Chemistry, University Park, University of Nottingham, Nottingham, NG7 2RD, United Kingdom.
3
Oxford Protein Production Factory, Research Complex at Harwell, Rutherford Appleton Laboratory, Oxfordshire, OX11 0FA, United Kingdom.
4
Department of Chemistry, University of Warwick, Gibbet Hill, Coventry, CV4 7AL, United Kingdom.
5
ISIS Neutron and Muon Source and Research Complex at Harwell, Rutherford Appleton Laboratory, Oxfordshire, OX11 0FA, United Kingdom.

Abstract

Ag(+) resistance was initially found on the Salmonella enetrica serovar Typhimurium multi-resistance plasmid pMG101 from burns patients in 1975. The putative model of Ag(+) resistance, encoded by the sil operon from pMG101, involves export of Ag(+) via an ATPase (SilP), an effluxer complex (SilCFBA) and a periplasmic chaperon of Ag(+) (SilE). SilE is predicted to be intrinsically disordered. We tested this hypothesis using structural and biophysical studies and show that SilE is an intrinsically disordered protein in its free apo-form but folds to a compact structure upon optimal binding to six Ag(+) ions in its holo-form. Sequence analyses and site-directed mutagenesis established the importance of histidine and methionine containing motifs for Ag(+) -binding, and identified a nucleation core that initiates Ag(+) -mediated folding of SilE. We conclude that SilE is a molecular sponge for absorbing metal ions.

PMID:
27085056
PMCID:
PMC5008109
DOI:
10.1111/mmi.13399
[Indexed for MEDLINE]
Free PMC Article

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