title: An aqueous H+ permeation pathway in the voltage-gated proton channel Hv1.
abstract: Hv1 voltage-gated proton channels mediate rapid and selective transmembrane H(+) flux and are gated by both voltage and pH gradients. Selective H(+) transfer in membrane proteins is commonly achieved by Grotthuss proton 'hopping' in chains of ionizable amino acid side chains and intraprotein water molecules. To identify whether ionizable residues are required for proton permeation in Hv1, we neutralized candidate residues and measured expressed voltage-gated H(+) currents. Unexpectedly, charge neutralization was insufficient to abrogate either the Hv1 conductance or coupling of pH gradient and voltage-dependent activation. Molecular dynamics simulations revealed water molecules in the central crevice of Hv1 model structures but not in homologous voltage-sensor domain (VSD) structures. Our results indicate that Hv1 most likely forms an internal water wire for selective proton transfer and that interactions between water molecules and S4 arginines may underlie coupling between voltage- and pH-gradient sensing.
authors.affiliation: Howard Hughes Medical Institute, Department of Cardiology and Manton Center for Orphan Disease, Children's Hospital Boston, Boston, Massachusetts, USA.|Department of Neurobiology, Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: I Scott
authors.initials: IS
authors.lastname: Ramsey
authors.affiliation: Department of Biochemistry, University of Oxford, Oxford, UK.
authors.forename: Younes
authors.initials: Y
authors.lastname: Mokrab
authors.affiliation: Howard Hughes Medical Institute, Department of Cardiology and Manton Center for Orphan Disease, Children's Hospital Boston, Boston, Massachusetts, USA.|Department of Neurobiology, Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Ingrid
authors.initials: I
authors.lastname: Carvacho
authors.affiliation: Department of Biochemistry, University of Oxford, Oxford, UK.
authors.forename: Zara A
authors.initials: ZA
authors.lastname: Sands
authors.affiliation: Department of Biochemistry, University of Oxford, Oxford, UK.
authors.forename: Mark S P
authors.initials: MSP
authors.lastname: Sansom
authors.affiliation: Howard Hughes Medical Institute, Department of Cardiology and Manton Center for Orphan Disease, Children's Hospital Boston, Boston, Massachusetts, USA.|Department of Neurobiology, Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: David E
authors.initials: DE
authors.lastname: Clapham
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D006801:Humans; D007473:Ion Channels / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D056004:Molecular Dynamics Simulation; D008969:Molecular Sequence Data; D009154:Mutation; D011487:Protein Conformation; D011522:Protons; D016415:Sequence Alignment; D014867:Water / Q000737:chemistry*
chemical_list: C510235:HVCN1 protein, human; D007473:Ion Channels; D011522:Protons; D014867:Water