title: Resting state of the human proton channel dimer in a lipid bilayer.
abstract: The voltage-gated proton channel Hv1 plays a critical role in the fast proton translocation that underlies a wide range of physiological functions, including the phagocytic respiratory burst, sperm motility, apoptosis, and metastatic cancer. Both voltage activation and proton conduction are carried out by a voltage-sensing domain (VSD) with strong similarity to canonical VSDs in voltage-dependent cation channels and enzymes. We set out to determine the structural properties of membrane-reconstituted human proton channel (hHv1) in its resting conformation using electron paramagnetic resonance spectroscopy together with biochemical and computational methods. We evaluated existing structural templates and generated a spectroscopically constrained model of the hHv1 dimer based on the Ci-VSD structure at resting state. Mapped accessibility data revealed deep water penetration through hHv1, suggesting a highly focused electric field, comprising two turns of helix along the fourth transmembrane segment. This region likely contains the H(+) selectivity filter and the conduction pore. Our 3D model offers plausible explanations for existing electrophysiological and biochemical data, offering an explicit mechanism for voltage activation based on a one-click sliding helix conformational rearrangement.
authors.affiliation: Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637 eperozo@uchicago.edu fqli@uchicago.edu.
authors.forename: Qufei
authors.initials: Q
authors.lastname: Li
authors.affiliation: Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637.
authors.forename: Rong
authors.initials: R
authors.lastname: Shen
authors.affiliation: Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637.
authors.forename: Jeremy S
authors.initials: JS
authors.lastname: Treger
authors.affiliation: Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637.
authors.forename: Sherry S
authors.initials: SS
authors.lastname: Wanderling
authors.affiliation: Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637.
authors.forename: Wieslawa
authors.initials: W
authors.lastname: Milewski
authors.affiliation: Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637.
authors.forename: Klaudia
authors.initials: K
authors.lastname: Siwowska
authors.affiliation: Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637.
authors.forename: Francisco
authors.initials: F
authors.lastname: Bezanilla
authors.affiliation: Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637 eperozo@uchicago.edu fqli@uchicago.edu.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Perozo
mesh_terms: D000595:Amino Acid Sequence; D019281:Dimerization; D006801:Humans; D015640:Ion Channel Gating; D007473:Ion Channels / Q000737:chemistry / Q000378:metabolism*; D008051:Lipid Bilayers; D008969:Molecular Sequence Data; D011522:Protons
chemical_list: D007473:Ion Channels; D008051:Lipid Bilayers; D011522:Protons
keywords: EPR; MD simulation; proton channel; voltage sensing domain