Letter | Published:

Aspartate 112 is the selectivity filter of the human voltage-gated proton channel

Nature volume 480, pages 273277 (08 December 2011) | Download Citation

Abstract

The ion selectivity of pumps and channels is central to their ability to perform a multitude of functions. Here we investigate the mechanism of the extraordinary selectivity of the human voltage-gated proton channel1, HV1 (also known as HVCN1). This selectivity is essential to its ability to regulate reactive oxygen species production by leukocytes2,3,4, histamine secretion by basophils5, sperm capacitation6, and airway pH7. The most selective ion channel known, HV1 shows no detectable permeability to other ions1. Opposing classes of selectivity mechanisms postulate that (1) a titratable amino acid residue in the permeation pathway imparts proton selectivity1,8,9,10,11, or (2) water molecules ‘frozen’ in a narrow pore conduct protons while excluding other ions12. Here we identify aspartate 112 as a crucial component of the selectivity filter of HV1. When a neutral amino acid replaced Asp 112, the mutant channel lost proton specificity and became anion-selective or did not conduct. Only the glutamate mutant remained proton-specific. Mutation of the nearby Asp 185 did not impair proton selectivity, indicating that Asp 112 has a unique role. Although histidine shuttles protons in other proteins, when histidine or lysine replaced Asp 112, the mutant channel was still anion-permeable. Evidently, the proton specificity of HV1 requires an acidic group at the selectivity filter.

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Acknowledgements

We thank P. H. Barry, D. Gillespie, V. S. Markin, J. F. Nagle, R. Pomès, D. Silverman and V. Sokolov for discussions or comments on the manuscript. Supported by NSF grant MCB-0943362 (S.M.E.S. and T.E.D.) and NIH grant GM087507 (T.E.D.). The content is solely the responsibility of the authors and does not necessarily represent the views of the National Institute of General Medical Sciences or the National Institutes of Health.

Author information

Author notes

    • Boris Musset
    •  & Susan M. E. Smith

    These authors contributed equally to this work.

Affiliations

  1. Department of Molecular Biophysics & Physiology, Rush University Medical Center, Chicago, Illinois 60612, USA

    • Boris Musset
    • , Deri Morgan
    • , Vladimir V. Cherny
    •  & Thomas E. DeCoursey
  2. Department of Pathology, Emory School of Medicine, Atlanta, Georgia 30322, USA

    • Susan M. E. Smith
  3. Department of Medicine, University of Chicago, Chicago, Illinois 60637, USA

    • Sindhu Rajan

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Contributions

S.R. identified the similarity of C15orf27 to HV1 and cloned the C15orf27 gene; S.M.E.S. conceived the strategic approach based on molecular model, sequence and phylogenetic analysis; S.R. and S.M.E.S. created mutants; T.E.D., B.M. and V.V.C. designed experiments; B.M., D.M. and V.V.C. recorded, analysed and interpreted data; T.E.D. wrote the manuscript; all authors read and approved the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Thomas E. DeCoursey.

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    Supplementary Information

    The file contains Supplementary Figures 1-9 with legends, Supplementary Tables 1-4 and additional references.

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DOI

https://doi.org/10.1038/nature10557

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