title: Arginine 116 stabilizes the entrance to the metal ion-binding site of the MntC protein.
abstract: The cyanobacterium Synechocystis sp. PCC 6803 imports Mn2+ ions via MntCAB, an ABC transport system that is expressed at submicromolar Mn2+ concentrations. The structures of the wild type (WT) and a site-directed mutant of the MntC solute-binding protein have been determined at 2.7 and 3.5 Å resolution, respectively. The WT structure is significantly improved over the previously determined structure (PDB entry 1xvl), showing improved Mn2+ binding site parameters, disulfide bonds in all three monomers and ions bound to the protein surface, revealing the role of Zn2+ ions in the crystallization liquor. The structure of MntC reveals that the active site is surrounded by neutral-to-positive electrostatic potential and is dominated by a network of polar interactions centred around Arg116. The mutation of this residue to alanine was shown to destabilize loops in the entrance to the metal-ion binding site and suggests a possible role in MntC function.
authors.affiliation: Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, Technion City, Haifa 32000, Israel.
authors.forename: Margarita
authors.initials: M
authors.lastname: Kanteev
authors.forename: Noam
authors.initials: N
authors.lastname: Adir
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000737:chemistry* / Q000235:genetics; D000409:Alanine / Q000737:chemistry / Q000235:genetics; D001120:Arginine / Q000737:chemistry / Q000235:genetics; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000737:chemistry / Q000235:genetics; D008345:Manganese / Q000737:chemistry*; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D055503:Protein Multimerization; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics; D055672:Static Electricity; D046939:Synechocystis / Q000737:chemistry* / Q000235:genetics; D015032:Zinc / Q000737:chemistry*
chemical_list: D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; D011994:Recombinant Proteins; D008345:Manganese; D001120:Arginine; D015032:Zinc; D000409:Alanine
keywords: ABC transporter; cyanobacteria; site-directed mutagenesis