title: Molecular mechanism of Zn2+ inhibition of a voltage-gated proton channel.
abstract: Voltage-gated proton (Hv1) channels are involved in many physiological processes, such as pH homeostasis and the innate immune response. Zn2+is an important physiological inhibitor of Hv1. Sperm cells are quiescent in the male reproductive system due to Zn2+inhibition of Hv1 channels, but become active once introduced into the low-Zn2+-concentration environment of the female reproductive tract. How Zn2+inhibits Hv1 is not completely understood. In this study, we use the voltage clamp fluorometry technique to identify the molecular mechanism of Zn2+inhibition of Hv1. We find that Zn2+binds to both the activated closed and resting closed states of the Hv1 channel, thereby inhibiting both voltage sensor motion and gate opening. Mutations of some Hv1 residues affect only Zn2+inhibition of the voltage sensor motion, whereas mutations of other residues also affect Zn2+inhibition of gate opening. These effects are similar in monomeric and dimeric Hv1 channels, suggesting that the Zn2+-binding sites are localized within each subunit of the dimeric Hv1. We propose that Zn2+binding has two major effects on Hv1: (i) at low concentrations, Zn2+binds to one site and prevents the opening conformational change of the pore of Hv1, thereby inhibiting proton conduction; and (ii) at high concentrations, Zn2+, in addition, binds to a second site and inhibits the outward movement of the voltage sensor of Hv1. Elucidating the molecular mechanism of how Zn2+inhibits Hv1 will further our understanding of Hv1 function and might provide valuable information for future drug development for Hv1 channels.
authors.affiliation: Department of Physiology and Biophysics, University of Miami, Miami, FL 33136.
authors.forename: Feng
authors.initials: F
authors.lastname: Qiu
authors.affiliation: Centre for Molecular Simulation, Department of Biological Sciences, University of Calgary, Calgary, AB, Canada T2N 2N4.
authors.forename: Adam
authors.initials: A
authors.lastname: Chamberlin
authors.affiliation: Department of Physiology and Biophysics, University of Miami, Miami, FL 33136.
authors.forename: Briana M
authors.initials: BM
authors.lastname: Watkins
authors.affiliation: Department of Physiology and Biophysics, University of Miami, Miami, FL 33136.
authors.forename: Alina
authors.initials: A
authors.lastname: Ionescu
authors.affiliation: Department of Physiology and Biophysics, University of Miami, Miami, FL 33136.
authors.forename: Marta Elena
authors.initials: ME
authors.lastname: Perez
authors.affiliation: Department of Physiology and Biophysics, University of Miami, Miami, FL 33136.
authors.forename: Rene
authors.initials: R
authors.lastname: Barro-Soria
authors.affiliation: Centro Interdisciplinario de Neurociencias de Valparaiso, Universidad de Valparaiso, Valparaíso 2366103, Chile.
authors.forename: Carlos
authors.initials: C
authors.lastname: González
authors.affiliation: Centre for Molecular Simulation, Department of Biological Sciences, University of Calgary, Calgary, AB, Canada T2N 2N4; plarsson@med.miami.edu snoskov@ucalgary.ca.
authors.forename: Sergei Y
authors.initials: SY
authors.lastname: Noskov
authors.affiliation: Department of Physiology and Biophysics, University of Miami, Miami, FL 33136; plarsson@med.miami.edu snoskov@ucalgary.ca.
authors.forename: H Peter
authors.initials: HP
authors.lastname: Larsson
mesh_terms: D000818:Animals; D001665:Binding Sites; D005260:Female; D005470:Fluorometry / Q000379:methods; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007113:Immunity, Innate / Q000235:genetics; D015640:Ion Channel Gating / Q000235:genetics*; D007473:Ion Channels / Q000235:genetics* / Q000378:metabolism; D009154:Mutation; D018408:Patch-Clamp Techniques / Q000379:methods; D011522:Protons; D014982:Xenopus laevis / Q000378:metabolism; D015032:Zinc / Q000737:chemistry / Q000378:metabolism*
chemical_list: C510235:HVCN1 protein, human; D007473:Ion Channels; D011522:Protons; D015032:Zinc
keywords: Hv1; Zn2+; inhibition; molecular model; voltage-gated proton channel