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PDBsum entry 6poj
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Transport protein
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PDB id
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6poj
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References listed in PDB file
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Key reference
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Title
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Structure of the functionally important extracellular loop c of human aquaporin 1 obtained by solid-State nmr under nearly physiological conditions.
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Authors
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D.A.Dingwell,
L.S.Brown,
V.Ladizhansky.
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Ref.
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J Phys Chem B, 2019,
123,
7700-7710.
[DOI no: ]
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PubMed id
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Abstract
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Human 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.
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