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An aqueous H+ permeation pathway in the voltage-gated proton channel Hv1

Nature Structural & Molecular Biology volume 17, pages 869–875 (2010)Cite this article

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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.

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Figure 1: Charge-neutralizing mutations in Hv1 conduct H+ current.
Figure 2: Voltage- and pH-gradient sensitivity of Hv1 mutations.
Figure 3: An aqueous crevice in the molecular dynamics–equilibrated Hv1 open-state homology model.
Figure 4: Water density in molecular dynamics simulations of Hv1 and other VS domains.
Figure 5: H+ permeation in Hv1 channels.

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Acknowledgements

We are grateful to J.W. Klingelhoefer for writing MATLAB script to calculate the water-count profiles, M.M. Moran and J.A. Chong for their invaluable support and critical insight and E. Ruchti for superb technical assistance. The Mental Retardation/Developmental Disabilities Research Center Molecular Genetics Core Facility at Children's Hospital is supported by US National Institutes of Health Grant P30-HD18655. Work in the Sansom laboratory is supported by grants from the UK Biotechnology and Biological Sciences Research Council and the Wellcome Trust.

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  1. I Scott Ramsey & Zara A Sands

    Present address: Present addresses: Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, Virginia, USA (I.S.R.) and UCB Pharma SA, Chemin Du Foriest, Braine-L'Alleud, Belgium (Z.A.S.).,

  2. I Scott Ramsey, Younes Mokrab and Ingrid Carvacho: These authors contributed equally to this work.

Authors and Affiliations

  1. Department of Cardiology and Manton Center for Orphan Disease, Howard Hughes Medical Institute, Children's Hospital Boston, Boston, Massachusetts, USA

    I Scott Ramsey, Ingrid Carvacho & David E Clapham

  2. Department of Neurobiology, Harvard Medical School, Boston, Massachusetts, USA

    I Scott Ramsey, Ingrid Carvacho & David E Clapham

  3. Department of Biochemistry, University of Oxford, Oxford, UK

    Younes Mokrab, Zara A Sands & Mark S P Sansom

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Contributions

I.S.R. and I.C. designed experiments, created Hv1 point mutations and performed electrophysiological experiments; Y.M. and Z.A.S. created Hv1 models and performed molecular dynamics simulations; D.E.C. and M.S.P.S. directed research activities; I.S.R., Y.M., Z.A.S., M.S.P.S. and D.E.C. wrote the paper.

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Ramsey, I., Mokrab, Y., Carvacho, I. et al. An aqueous H+ permeation pathway in the voltage-gated proton channel Hv1. Nat Struct Mol Biol 17, 869–875 (2010). https://doi.org/10.1038/nsmb.1826

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