title: Lipid-protein interactions in double-layered two-dimensional AQP0 crystals.
abstract: Lens-specific aquaporin-0 (AQP0) functions as a specific water pore and forms the thin junctions between fibre cells. Here we describe a 1.9 A resolution structure of junctional AQP0, determined by electron crystallography of double-layered two-dimensional crystals. Comparison of junctional and non-junctional AQP0 structures shows that junction formation depends on a conformational switch in an extracellular loop, which may result from cleavage of the cytoplasmic amino and carboxy termini. In the centre of the water pathway, the closed pore in junctional AQP0 retains only three water molecules, which are too widely spaced to form hydrogen bonds with each other. Packing interactions between AQP0 tetramers in the crystalline array are mediated by lipid molecules, which assume preferred conformations. We were therefore able to build an atomic model for the lipid bilayer surrounding the AQP0 tetramers, and we describe lipid-protein interactions.
authors.affiliation: Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, Massachusetts 02115, USA.
authors.forename: Tamir
authors.initials: T
authors.lastname: Gonen
authors.forename: Yifan
authors.initials: Y
authors.lastname: Cheng
authors.forename: Piotr
authors.initials: P
authors.lastname: Sliz
authors.forename: Yoko
authors.initials: Y
authors.lastname: Hiroaki
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Fujiyoshi
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Harrison
authors.forename: Thomas
authors.initials: T
authors.lastname: Walz
mesh_terms: D000818:Animals; D020346:Aquaporins / Q000737:chemistry* / Q000378:metabolism*; D003460:Crystallization; D003461:Crystallography; D006860:Hydrogen Bonding; D007908:Lens, Crystalline / Q000737:chemistry; D008051:Lipid Bilayers / Q000737:chemistry / Q000378:metabolism; D008563:Membrane Lipids / Q000378:metabolism*; D008958:Models, Molecular; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D012756:Sheep; D014867:Water / Q000032:analysis / Q000737:chemistry
chemical_list: D020346:Aquaporins; D008051:Lipid Bilayers; D008563:Membrane Lipids; D014867:Water