title: The MerR metalloregulatory protein binds mercuric ion as a tricoordinate, metal-bridged dimer.
abstract: Bacterial MerR proteins are dimeric DNA-binding proteins that mediate the Hg(II)-dependent induction of mercury resistance operons. Site-directed mutagenesis of the Bacillus sp. RC607 MerR protein reveals that three of four Cys residues per monomer are required for Hg(II) binding at the single high-affinity binding site. Inactive mutant homodimers can exchange subunits to form heterodimers active for Hg(II) binding. Studies of a heterodimer retaining only three of eight cysteine residues per dimer reveal that Cys79 in one subunit and Cys114 and Cys123 in the second subunit are necessary and sufficient for high-affinity Hg(II) binding in an asymmetric, subunit bridging coordination complex.
authors.affiliation: Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115.
authors.forename: J D
authors.initials: JD
authors.lastname: Helmann
authors.forename: B T
authors.initials: BT
authors.lastname: Ballard
authors.forename: C T
authors.initials: CT
authors.lastname: Walsh
mesh_terms: D000595:Amino Acid Sequence; D001407:Bacillus / Q000032:analysis* / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites; D002412:Cations; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D046911:Macromolecular Substances; D008628:Mercury / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D013329:Structure-Activity Relationship
chemical_list: D001426:Bacterial Proteins; D002412:Cations; D004268:DNA-Binding Proteins; D046911:Macromolecular Substances; C051124:MerR protein, Bacteria; D008628:Mercury