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STRUCTURAL REFINEMENT OF AQUAPORIN 1 VIA SSNMR
Structural highlights
FunctionAQP1_HUMAN Forms a water-specific channel that provides the plasma membranes of red cells and kidney proximal tubules with high permeability to water, thereby permitting water to move in the direction of an osmotic gradient.[1] Publication Abstract from PubMedHuman aquaporin 1 (hAQP1) is the first discovered selective water channel present in lipid membranes of multiple types of cells. Several structures of hAQP1 and its bovine homolog have been obtained by electron microscopy and X-ray crystallography, giving a consistent picture of the transmembrane domain with the water-conducting pore. The transmembrane domain is formed by six full helices and two half-helices, which form a central constriction with conserved asparagine-proline-alanine motifs. Another constriction, the aromatic/arginine (ar/R) filter, is found close to the extracellular surface, and includes aromatic residues and a conserved arginine (Arg-195). Although the existing crystal structures largely converge on the location of helical segments, they differ in details of conformation of the longest extracellular loop C and its interactions with the ar/R filter (in particular, with Arg-195). Here, we use solid-state nuclear magnetic resonance to determine multiple interatomic distances, and come up with a refined structural model for hAQP1, which represents a physiologically relevant state predominant at noncryogenic temperatures in a lipid environment. The model clearly disambiguates the position of the Arg-195 sidechain disputed previously and shows a number of interactions for loop C, both with the ar/R filter and a number of other residues on the extracellular side of hAQP1. Structure of the Functionally Important Extracellular Loop C of Human Aquaporin 1 Obtained by Solid-State NMR under Nearly Physiological Conditions.,Dingwell DA, Brown LS, Ladizhansky V J Phys Chem B. 2019 Sep 12;123(36):7700-7710. doi: 10.1021/acs.jpcb.9b06430. Epub, 2019 Aug 27. PMID:31411472[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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