title: Crystal Structure and Conformational Change Mechanism of a Bacterial Nramp-Family Divalent Metal Transporter.
abstract: The widely conserved natural resistance-associated macrophage protein (Nramp) family of divalent metal transporters enables manganese import in bacteria and dietary iron uptake in mammals. We determined the crystal structure of the Deinococcus radiodurans Nramp homolog (DraNramp) in an inward-facing apo state, including the complete transmembrane (TM) segment 1a (absent from a previous Nramp structure). Mapping our cysteine accessibility scanning results onto this structure, we identified the metal-permeation pathway in the alternate outward-open conformation. We investigated the functional impact of two natural anemia-causing glycine-to-arginine mutations that impaired transition metal transport in both human Nramp2 and DraNramp. The TM4 G153R mutation perturbs the closing of the outward metal-permeation pathway and alters the selectivity of the conserved metal-binding site. In contrast, the TM1a G45R mutation prevents conformational change by sterically blocking the essential movement of that helix, thus locking the transporter in an inward-facing state.
authors.affiliation: Department of Molecular and Cellular Biology, Harvard University, 52 Oxford Street, Cambridge, MA 02138, USA.
authors.forename: Aaron T
authors.initials: AT
authors.lastname: Bozzi
authors.affiliation: Department of Molecular and Cellular Biology, Harvard University, 52 Oxford Street, Cambridge, MA 02138, USA.
authors.forename: Lukas B
authors.initials: LB
authors.lastname: Bane
authors.affiliation: Department of Molecular and Cellular Biology, Harvard University, 52 Oxford Street, Cambridge, MA 02138, USA.
authors.forename: Wilhelm A
authors.initials: WA
authors.lastname: Weihofen
authors.affiliation: Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
authors.forename: Abhishek
authors.initials: A
authors.lastname: Singharoy
authors.affiliation: Whitehead Institute for Biomedical Research, Nine Cambridge Center, Cambridge, MA 02142, USA.
authors.forename: Eduardo R
authors.initials: ER
authors.lastname: Guillen
authors.affiliation: Whitehead Institute for Biomedical Research, Nine Cambridge Center, Cambridge, MA 02142, USA.
authors.forename: Hidde L
authors.initials: HL
authors.lastname: Ploegh
authors.affiliation: Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Department of Physics, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
authors.forename: Klaus
authors.initials: K
authors.lastname: Schulten
authors.affiliation: Department of Molecular and Cellular Biology, Harvard University, 52 Oxford Street, Cambridge, MA 02138, USA. Electronic address: gaudet@mcb.harvard.edu.
authors.forename: Rachelle
authors.initials: R
authors.lastname: Gaudet
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D027682:Cation Transport Proteins / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D018360:Crystallography, X-Ray; D034301:Deinococcus / Q000235:genetics / Q000378:metabolism*; D008670:Metals / Q000378:metabolism*; D008958:Models, Molecular; D009154:Mutation; D011485:Protein Binding; D000099173:Natural Resistance-associated Macrophage Protein 1
chemical_list: D001426:Bacterial Proteins; D027682:Cation Transport Proteins; D008670:Metals; D000099173:Natural Resistance-associated Macrophage Protein 1
keywords: LeuT fold; MntH; Nramp; crystallography; cysteine accessibility; divalent metal transporter; microcytic anemia; natural resistance-associated macrophage protein; transition metals