Letter

Aquaporin-0 membrane junctions reveal the structure of a closed water pore

Received:
Accepted:
Published online:

Abstract

The lens-specific water pore aquaporin-0 (AQP0) is the only aquaporin known to form membrane junctions in vivo1. We show here that AQP0 from the lens core, containing some carboxy-terminally cleaved AQP02,3, forms double-layered crystals that recapitulate in vivo junctions. We present the structure of the AQP0 membrane junction as determined by electron crystallography. The junction is formed by three localized interactions between AQP0 molecules in adjoining membranes, mainly mediated by proline residues conserved in AQP0s from different species but not present in most other aquaporins. Whereas all previously determined aquaporin structures show the pore in an open conformation4,5,6,7,8,9, the water pore is closed in AQP0 junctions. The water pathway in AQP0 also contains an additional pore constriction, not seen in other known aquaporin structures4,5,6,7,8,9, which may be responsible for pore gating.

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Acknowledgements

We thank S. C. Harrison for help with the molecular replacement, model building and writing of the manuscript. We also thank Y. Fujiyoshi, K. Mitsuoka and K. Tani for advice. This work was supported by National Institute of Health funding to T.W.

Author information

Affiliations

  1. Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, Massachusetts 02115, USA

    • Tamir Gonen
    • , Yifan Cheng
    •  & Thomas Walz
  2. Howard Hughes Medical Institute and Children's Hospital Laboratory of Molecular Medicine, 320 Longwood Avenue, and Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 240 Longwood Avenue, Boston, Massachusetts 02115, USA

    • Piotr Sliz
  3. School of Biological Sciences, University of Auckland, Auckland PO Box 92019, New Zealand

    • Joerg Kistler

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Competing interests

The authors declare that they have no competing financial interests.

Corresponding author

Correspondence to Thomas Walz.

Supplementary information

Image files

  1. 1.

    Supplementary Figure 1

    Stereo view of the density modified map showing residues lining the closed water pore.

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