title: Crystallographic evidence of a large ligand-induced hinge-twist motion between the two domains of the maltodextrin binding protein involved in active transport and chemotaxis.
abstract: The periplasmic maltodextrin binding protein of Escherichia coli serves as an initial receptor for the active transport of and chemotaxis toward maltooligosaccharides. The three-dimensional structure of the binding protein complexed with maltose has been previously reported [Spurlino, J. C., Lu, G.-Y., & Quiocho, F. A. (1991) J. Biol. Chem. 266, 5202-5219]. Here we report the structure of the unliganded form of the binding protein refined to 1.8-A resolution. This structure, combined with that for the liganded form, provides the first crystallographic evidence that a major ligand-induced conformational change occurs in a periplasmic binding protein. The unliganded structure shows a rigid-body "hinge-bending" between the two globular domains by approximately 35 degrees, relative to the maltose-bound structure, opening the sugar binding site groove located between the two domains. In addition, there is an 8 degrees twist of one domain relative to the other domain. The conformational changes observed between this structure and the maltose-bound structure are consistent with current models of maltose/maltodextrin transport and maltose chemotaxis and solidify a mechanism for receptor differentiation between the ligand-free and ligand-bound forms in signal transduction.
authors.affiliation: Howard Hughes Medical Institute, Baylor College of Medicine, Houston, Texas 77030.
authors.forename: A J
authors.initials: AJ
authors.lastname: Sharff
authors.forename: L E
authors.initials: LE
authors.lastname: Rodseth
authors.forename: J C
authors.initials: JC
authors.lastname: Spurlino
authors.forename: F A
authors.initials: FA
authors.lastname: Quiocho
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D001693:Biological Transport, Active; D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism; D002633:Chemotaxis; D003460:Crystallization; D004926:Escherichia coli / Q000737:chemistry*; D029968:Escherichia coli Proteins; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015394:Molecular Structure; D033902:Periplasmic Binding Proteins; D011487:Protein Conformation; D014961:X-Ray Diffraction
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; C461619:MalE protein, E coli; D033902:Periplasmic Binding Proteins