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


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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Figure 1: Double-layered two-dimensional crystals of AQP0.
Figure 2: The AQP0-mediated membrane junction.
Figure 3: The closed AQP0 water pore.

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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.

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Correspondence to Thomas Walz.

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Supplementary Figure 1

Stereo view of the density modified map showing residues lining the closed water pore. (JPG 173 kb)

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Gonen, T., Sliz, P., Kistler, J. et al. Aquaporin-0 membrane junctions reveal the structure of a closed water pore. Nature 429, 193–197 (2004).

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