2zz9
From Proteopedia
Structure of aquaporin-4 S180D mutant at 2.8 A resolution by electron crystallography
Structural highlights
FunctionAQP4_RAT Forms a water-specific channel. Osmoreceptor which regulates body water balance and mediates water flow within the central nervous system. It is expressed predominantly in the ependymal cell lining the aqueductal system and over the space of the brain in contact with the subarachnoid space, as cerebrospinal fluid fills these structures it may facilitate water balance between brain parenchyma and the fluid compartment. In the plasma membranes of the neurons of the paraventricular and supraoptic nuclei, it may mediate rapid changes in cell volume in response to local shifts in extracellular osmolarity. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedMembers of the aquaporin (AQP) family are expressed in almost every organism, including 13 homologues in humans. Based on the electron crystallographic structure of AQP1, the hydrogen-bond isolation mechanism was proposed to explain why AQPs are impermeable to protons despite their very fast water conduction. The mechanism by which AQPs exclude protons remained controversial, however. Here we present the structure of AQP4 at 2.8 A resolution obtained by electron crystallography of double-layered two-dimensional crystals. The resolution has been improved from the previous 3.2 A, with accompanying improvement in data quality resulting in the ability to identify individual water molecules. Our structure of AQP4, the predominant water channel in the brain, reveals eight water molecules in the channel. The arrangement of the waters provides support for the hydrogen-bond isolation mechanism. Our AQP4 structure also visualizes five lipids, showing that direct interactions of the extracellular surface of AQP4 with three lipids in the adjoining membrane help stabilize the membrane junction. Mechanism of aquaporin-4's fast and highly selective water conduction and proton exclusion.,Tani K, Mitsuma T, Hiroaki Y, Kamegawa A, Nishikawa K, Tanimura Y, Fujiyoshi Y J Mol Biol. 2009 Jun 19;389(4):694-706. Epub 2009 May 3. PMID:19406128[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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