title: X-ray structures of the leucine-binding protein illustrate conformational changes and the basis of ligand specificity.
abstract: The periplasmic leucine-binding protein is the primary receptor for the leucine transport system in Escherichia coli. We report here the structure of an open ligand-free form solved by molecular replacement and refined at 1.5-A resolution. In addition, two closed ligand-bound structures of the same protein are presented, a phenylalanine-bound form at 1.8 A and a leucine-bound structure at a nominal resolution of 2.4 A. These structures show the basis of this protein's ligand specificity, as well as illustrating the conformational changes that are associated with ligand binding. Comparison with earlier structures provides further information about solution conformations, as well as the different specificity of the closely related leucine/isoleucine/valine-binding protein.
authors.affiliation: Department of Cell and Molecular Biology, Uppsala University, Biomedical Center, Box 596, S-751 24 Uppsala, Sweden.
authors.forename: Ulrika
authors.initials: U
authors.lastname: Magnusson
authors.forename: Branka
authors.initials: B
authors.lastname: Salopek-Sondi
authors.forename: Linda A
authors.initials: LA
authors.lastname: Luck
authors.forename: Sherry L
authors.initials: SL
authors.lastname: Mowbray
mesh_terms: D001665:Binding Sites; D004926:Escherichia coli; D029968:Escherichia coli Proteins; D008024:Ligands; D033902:Periplasmic Binding Proteins / Q000737:chemistry*; D011487:Protein Conformation; D013329:Structure-Activity Relationship; D014961:X-Ray Diffraction
chemical_list: D029968:Escherichia coli Proteins; D008024:Ligands; C024913:LivK protein, E coli; D033902:Periplasmic Binding Proteins