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

• Published in: Nature Vol. 429; no. 6988; pp. 193 - 197
• Main Authors: Walz, Thomas, Gonen, Tamir, Sliz, Piotr, Kistler, Joerg, Cheng, Yifan
• Format: Journal Article
• Language: English
• Published: London Nature Publishing 13-05-2004; Nature Publishing Group
• Subjects: Animals; Aquaporins; Biological and medical sciences; Biological Transport; Cell Membrane - metabolism; Cell Membrane - ultrastructure; Cell Membrane Permeability; Cryoelectron Microscopy; Crystalline structure; Crystallization; Crystallography; Crystals; Electric Conductivity; Eye Proteins - chemistry; Eye Proteins - isolation & purification; Eye Proteins - metabolism; Eye Proteins - ultrastructure; Fundamental and applied biological sciences. Psychology; Hydrogen-Ion Concentration; Lens, Crystalline - chemistry; Membrane Glycoproteins - chemistry; Membrane Glycoproteins - isolation & purification; Membrane Glycoproteins - metabolism; Membrane Glycoproteins - ultrastructure; Membranes; Models, Molecular; Molecular biophysics; Molecular Sequence Data; Molecules; Protein Conformation; Sheep; Structure in molecular biology; Water; Water - metabolism; Aquaporin; Crystalline structure
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/nature02503

The lens-specific water pore aquaporin-0 (AQP0) is the only aquaporin known to form membrane junctions in vivo. We show here that AQP0 from the lens core, containing some carboxy-terminally cleaved AQP0, 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 conformation, 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 structures, which may be responsible for pore gating.