title: Structural basis of gating by the outer membrane transporter FecA.
abstract: Siderophore-mediated acquisition systems facilitate iron uptake. We present the crystallographic structure of the integral outer membrane receptor FecA from Escherichia coli with and without ferric citrate at 2.5 and 2.0 angstrom resolution. FecA is composed of three distinct domains: the barrel, plug, and NH2-terminal extension. Binding of ferric citrate triggers a conformational change of the extracellular loops that close the external pocket of FecA. Ligand-induced allosteric transitions are propagated through the outer membrane by the plug domain, signaling the occupancy of the receptor in the periplasm. These data establish the structural basis of gating for receptors dependent on the cytoplasmic membrane protein TonB. By compiling available data for this family of receptors, we propose a mechanism for the energy-dependent transport of siderophores.
authors.affiliation: Howard Hughes Medical Institute and Department of Biochemistry, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390, USA.
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Ferguson
authors.forename: Ranjan
authors.initials: R
authors.lastname: Chakraborty
authors.forename: Barbara S
authors.initials: BS
authors.lastname: Smith
authors.forename: Lothar
authors.initials: L
authors.lastname: Esser
authors.forename: Dick
authors.initials: D
authors.lastname: van der Helm
authors.forename: Johann
authors.initials: J
authors.lastname: Deisenhofer
mesh_terms: D000327:Adsorption; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism; D001665:Binding Sites; D001693:Biological Transport, Active; D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D018360:Crystallography, X-Ray; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism; D005290:Ferric Compounds / Q000378:metabolism*; D006860:Hydrogen Bonding; D015640:Ion Channel Gating; D008024:Ligands; D008565:Membrane Proteins / Q000378:metabolism; D008958:Models, Molecular; D011485:Protein Binding; D011487:Protein Conformation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011956:Receptors, Cell Surface; D017262:Siderophores / Q000378:metabolism*; D055672:Static Electricity
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; C028589:FecA protein, E coli; D005290:Ferric Compounds; D008024:Ligands; D008565:Membrane Proteins; D011956:Receptors, Cell Surface; D017262:Siderophores; C057616:tonB protein, Bacteria; C489181:tonB protein, E coli; C025314:ferric citrate