Hg(II) sequestration and protection by the MerR metal-binding domain (MBD).
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.
Qin
Jie
J
Department of Microbiology and the Center for Metalloenzyme Studies, University of Georgia, Athens, GA 30602-2605, USA.
Song
Lingyun
L
Department of Microbiology and the Center for Metalloenzyme Studies, University of Georgia, Athens, GA 30602-2605, USA.
Brim
Hassan
H
Department of Pathology, Uniformed Services University of the Health Sciences, Bethesda, MD 20814-4799, USA.
Daly
Michael J
MJ
Department of Pathology, Uniformed Services University of the Health Sciences, Bethesda, MD 20814-4799, USA.
Summers
Anne O
AO
Department of Microbiology and the Center for Metalloenzyme Studies, University of Georgia, Athens, GA 30602-2605, USA.
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
D001426:Bacterial Proteins; D003470:Culture Media; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C051124:MerR protein, Bacteria; D002104:Cadmium; D008628:Mercury; D015032:Zinc