title: Mechanism of Na+/H+ antiporting.
abstract: Na+/H+ antiporters are central to cellular salt and pH homeostasis. The structure of Escherichia coli NhaA was recently determined, but its mechanisms of transport and pH regulation remain elusive. We performed molecular dynamics simulations of NhaA that, with existing experimental data, enabled us to propose an atomically detailed model of antiporter function. Three conserved aspartates are key to our proposed mechanism: Asp164 (D164) is the Na+-binding site, D163 controls the alternating accessibility of this binding site to the cytoplasm or periplasm, and D133 is crucial for pH regulation. Consistent with experimental stoichiometry, two protons are required to transport a single Na+ ion: D163 protonates to reveal the Na+-binding site to the periplasm, and subsequent protonation of D164 releases Na+. Additional mutagenesis experiments further validated the model.
authors: D. E. Shaw Research, New York, NY 10036, USA.
authors: Isaiah T
authors: IT
authors: Arkin
authors: Huafeng
authors: H
authors: Xu
authors: Morten Ø
authors: MØ
authors: Jensen
authors: Eyal
authors: E
authors: Arbely
authors: Estelle R
authors: ER
authors: Bennett
authors: Kevin J
authors: KJ
authors: Bowers
authors: Edmond
authors: E
authors: Chow
authors: Ron O
authors: RO
authors: Dror
authors: Michael P
authors: MP
authors: Eastwood
authors: Ravenna
authors: R
authors: Flitman-Tene
authors: Brent A
authors: BA
authors: Gregersen
authors: John L
authors: JL
authors: Klepeis
authors: István
authors: I
authors: Kolossváry
authors: Yibing
authors: Y
authors: Shan
authors: David E
authors: DE
authors: Shaw
mesh_terms: D001224:Aspartic Acid / Q000378:metabolism; D001665:Binding Sites; D003198:Computer Simulation; D003460:Crystallization; D003593:Cytoplasm / Q000378:metabolism; D004926:Escherichia coli / Q000254:growth & development / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism*; D006860:Hydrogen Bonding; D006863:Hydrogen-Ion Concentration; D017136:Ion Transport; D008954:Models, Biological; D008958:Models, Molecular; D016296:Mutagenesis; D019897:Periplasm / Q000378:metabolism; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D011522:Protons; D012964:Sodium / Q000378:metabolism*; D017923:Sodium-Hydrogen Exchangers / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D029968:Escherichia coli Proteins; C102839:NhaA protein, E coli; D011522:Protons; D017923:Sodium-Hydrogen Exchangers; D001224:Aspartic Acid; D012964:Sodium