title: Structure of the manganese-bound manganese transport regulator of Bacillus subtilis.
abstract: The Bacillus subtilis manganese transport regulator, MntR, binds Mn2+ as an effector and is a repressor of transporters that import manganese. A member of the diphtheria toxin repressor (DtxR) family of metalloregulatory proteins, MntR exhibits selectivity for Mn2+ over Fe2+. Replacement of a metal-binding residue, Asp8, with methionine (D8M) relaxes this specificity. We report here the X-ray crystal structures of wild-type MntR and the D8M mutant bound to manganese with 1.75 A and 1.61 A resolution, respectively. The 142-residue MntR homodimer has substantial structural similarity to the 226-residue DtxR but lacks the C-terminal SH3-like domain of DtxR. The metal-binding pockets of MntR and DtxR are substantially different. The cation-to-cation distance between the two manganese ions bound by MntR is 3.3 A, whereas that between the metal ions bound by DtxR is 9 A. D8M binds only a single Mn2+ per monomer, owing to alteration of the metal-binding site. The sole retained metal site adopts pseudo-hexacoordinate geometry rather than the pseudo-heptacoordinate geometry of the MntR metal sites.
authors.affiliation: Department of Chemistry, Reed College, 3203 SE Woodstock Blvd., Portland, Oregon 97202, USA. glasfeld@reed.edu
authors.forename: Arthur
authors.initials: A
authors.lastname: Glasfeld
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Guedon
authors.forename: John D
authors.initials: JD
authors.lastname: Helmann
authors.forename: Richard G
authors.initials: RG
authors.lastname: Brennan
mesh_terms: D000595:Amino Acid Sequence; D001412:Bacillus subtilis / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins; D020134:Catalytic Domain / Q000235:genetics; D018360:Crystallography, X-Ray; D008345:Manganese / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D055672:Static Electricity
chemical_list: D001426:Bacterial Proteins; C433792:MntR protein, bacteria; D011994:Recombinant Proteins; D012097:Repressor Proteins; D008345:Manganese