title: The core metal-recognition domain of MerR.
abstract: MerR, the metalloregulatory protein of the mercury-resistance operon (mer) has unusually high affinity and specificity for ionic mercury, Hg(II). Prior genetic and biochemical evidence suggested that the protein has a structure consisting of an N-terminal DNA binding domain, a C-terminal Hg(II)-binding domain, and an intervening region involved with communication between these two domains. We have characterized a series of MerR deletion mutants and found that as little as 30% of the protein (residues 80-128) forms a stable dimer and retains high affinity for Hg(II). Biophysical measures indicate that this minimal Hg(II)-binding domain assumes the structural characteristics of the wild-type full-length protein both in the Hg(II) center itself and in an immediately adjacent helical protein domain. Our observations are consistent with the core Hg(II)-binding domain of the MerR dimer being constituted by a pair of antiparallel helices (possibly in a coiled-coil conformation) comprised of residues cysteine 82 through cysteine 117 from each monomer followed by a flexible loop through residue cysteine 126. These antiparallel helices would have a potential Hg(II)-binding site at each end. However, just as in the full-length protein, only one of these potential binding sites in the deleted proteins actually binds Hg(II).
authors.affiliation: The Department of Microbiology, University of Georgia, Athens 30602, USA.
authors.forename: Q
authors.initials: Q
authors.lastname: Zeng
authors.forename: C
authors.initials: C
authors.lastname: Stålhandske
authors.forename: M C
authors.initials: MC
authors.lastname: Anderson
authors.forename: R A
authors.initials: RA
authors.lastname: Scott
authors.forename: A O
authors.initials: AO
authors.lastname: Summers
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D002942:Circular Dichroism; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D019281:Dimerization; D004352:Drug Resistance, Microbial; D006639:Histidine / Q000235:genetics; D013058:Mass Spectrometry; D008628:Mercury / Q000737:chemistry* / Q000378:metabolism; D008969:Molecular Sequence Data; D011485:Protein Binding / Q000235:genetics; D017433:Protein Structure, Secondary; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000138:chemical synthesis / Q000302:isolation & purification; D017384:Sequence Deletion; D013057:Spectrum Analysis; D014965:X-Rays
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C051124:MerR protein, Bacteria; D011993:Recombinant Fusion Proteins; D006639:Histidine; D008628:Mercury