title: Hg(II) sequestration and protection by the MerR metal-binding domain (MBD).
abstract: MerR, the metalloregulator of the bacterial mercury resistance (mer) operon, binds Hg(II) with high affinity. To study the mechanism of metal-induced activation, a small protein was previously engineered embodying in a single polypeptide the metal-binding domain (MBD) ordinarily formed between two monomers of MerR. Here the physiological and biochemical properties of MBD expressed on the cell surface or in the cytosol were examined, to better understand the environments in which specific metal binding can occur with this small derivative. Over 20 000 surface copies of MBD were expressed per Escherichia coli cell, with metal stoichiometries of approximately 1.0 Hg(II) per MBD monomer. Cells expressing MBD on their surface in rich medium bound 6.1-fold more Hg(II) than those not expressing MBD. Although in nature cells use the entire mer operon to detoxify mercury, it was interesting to note that cells expressing only MBD survived Hg(II) challenge and recovered more quickly than cells without MBD. Cell-surface-expressed MBD bound Hg(II) preferentially even in the presence of a 22-fold molar excess of Zn(II) and when exposed to equimolar Cd(II) in addition. MBD expressed in the cystosol also afforded improved survival from Hg(II) exposure for E. coli and for the completely unrelated bacterium Deinococcus radiodurans.
authors.affiliation: Department of Microbiology and the Center for Metalloenzyme Studies, University of Georgia, Athens, GA 30602-2605, USA.
authors.forename: Jie
authors.initials: J
authors.lastname: Qin
authors.affiliation: Department of Microbiology and the Center for Metalloenzyme Studies, University of Georgia, Athens, GA 30602-2605, USA.
authors.forename: Lingyun
authors.initials: L
authors.lastname: Song
authors.affiliation: Department of Pathology, Uniformed Services University of the Health Sciences, Bethesda, MD 20814-4799, USA.
authors.forename: Hassan
authors.initials: H
authors.lastname: Brim
authors.affiliation: Department of Pathology, Uniformed Services University of the Health Sciences, Bethesda, MD 20814-4799, USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Daly
authors.affiliation: Department of Microbiology and the Center for Metalloenzyme Studies, University of Georgia, Athens, GA 30602-2605, USA.
authors.forename: Anne O
authors.initials: AO
authors.lastname: Summers
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D001665:Binding Sites; D002104:Cadmium / Q000378:metabolism / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism; D003470:Culture Media; D003600:Cytosol / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000378:metabolism*; D034301:Deinococcus / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism; D004926:Escherichia coli / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D008628:Mercury / Q000378:metabolism* / Q000494:pharmacology; D015032:Zinc / Q000378:metabolism / Q000494:pharmacology
chemical_list: D001426:Bacterial Proteins; D003470:Culture Media; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C051124:MerR protein, Bacteria; D002104:Cadmium; D008628:Mercury; D015032:Zinc