title: Structural analysis of the choline-binding protein ChoX in a semi-closed and ligand-free conformation.
abstract: The periplasmic ligand-binding protein ChoX is part of the ABC transport system ChoVWX that imports choline as a nutrient into the soil bacterium Sinorhizobium meliloti. We have recently reported the crystal structures of ChoX in complex with its ligands choline and acetylcholine and the structure of a fully closed but substrate-free state of ChoX. This latter structure revealed an architecture of the ligand-binding site that is superimposable to the closed, ligand-bound form of ChoX. We report here the crystal structure of ChoX in an unusual, ligand-free conformation that represents a semi-closed form of ChoX. The analysis revealed a subdomain movement in the N-lobe of ChoX. Comparison with the two well-characterized substrate binding proteins, MBP and HisJ, suggests the presence of a similar subdomain in these proteins.
authors: Institute of Biochemistry, Heinrich Heine University Düsseldorf, Universitätsstr. 1, D-40225 Düsseldorf, Germany.
authors: Christine
authors: C
authors: Oswald
authors: Sander H J
authors: SH
authors: Smits
authors: Marina
authors: M
authors: Höing
authors: Erhard
authors: E
authors: Bremer
authors: Lutz
authors: L
authors: Schmitt
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D002794:Choline / Q000378:metabolism*; D018360:Crystallography, X-Ray; D008024:Ligands; D056004:Molecular Dynamics Simulation; D009068:Movement; D033902:Periplasmic Binding Proteins / Q000737:chemistry* / Q000378:metabolism*; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D016962:Sinorhizobium meliloti
chemical_list: D001426:Bacterial Proteins; D008024:Ligands; D033902:Periplasmic Binding Proteins; D002794:Choline