title: High-resolution x-ray structure of human aquaporin 5.
abstract: Human aquaporin 5 (HsAQP5) facilitates the transport of water across plasma membranes and has been identified within cells of the stomach, duodenum, pancreas, airways, lungs, salivary glands, sweat glands, eyes, lacrimal glands, and the inner ear. AQP5, like AQP2, is subject to posttranslational regulation by phosphorylation, at which point it is trafficked between intracellular storage compartments and the plasma membrane. Details concerning the molecular mechanism of membrane trafficking are unknown. Here we report the x-ray structure of HsAQP5 to 2.0-A resolution and highlight structural similarities and differences relative to other eukaryotic aquaporins. A lipid occludes the putative central pore, preventing the passage of gas or ions through the center of the tetramer. Multiple consensus phosphorylation sites are observed in the structure and their potential regulatory role is discussed. We postulate that a change in the conformation of the C terminus may arise from the phosphorylation of AQP5 and thereby signal trafficking.
authors.affiliation: Department of Chemistry, Biochemistry and Biophysics, University of Gothenburg, Box 462, SE-405 30 Göteborg, Sweden.
authors.forename: Rob
authors.initials: R
authors.lastname: Horsefield
authors.forename: Kristina
authors.initials: K
authors.lastname: Nordén
authors.forename: Maria
authors.initials: M
authors.lastname: Fellert
authors.forename: Anna
authors.initials: A
authors.lastname: Backmark
authors.forename: Susanna
authors.initials: S
authors.lastname: Törnroth-Horsefield
authors.forename: Anke C
authors.initials: AC
authors.lastname: Terwisscha van Scheltinga
authors.forename: Jan
authors.initials: J
authors.lastname: Kvassman
authors.forename: Per
authors.initials: P
authors.lastname: Kjellbom
authors.forename: Urban
authors.initials: U
authors.lastname: Johanson
authors.forename: Richard
authors.initials: R
authors.lastname: Neutze