Open AccessArginine 116 stabilizes the entrance to the metal ion‐binding site of the MntC protein
Author(s) -
Kanteev Margarita,
Adir Noam
Publication year - 2013
Publication title -
acta crystallographica section f
Language(s) - English
Resource type - Journals
ISSN - 1744-3091
DOI - 10.1107/s174430911300153x
Subject(s) - binding site , alanine , chemistry , crystallography , crystallization , metal ions in aqueous solution , ion , active site , metal , mutant , a site , protein structure , residue (chemistry) , crystal structure , biophysics , stereochemistry , amino acid , biochemistry , biology , enzyme , organic chemistry , gene
The cyanobacterium Synechocystis sp. PCC 6803 imports Mn 2+ ions via MntCAB, an ABC transport system that is expressed at submicromolar Mn 2+ 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 Mn 2+ binding site parameters, disulfide bonds in all three monomers and ions bound to the protein surface, revealing the role of Zn 2+ 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.