Architecture and Selectivity in Aquaporins: 2.5 Å X-Ray Structure of Aquaporin Z

Savage, David F.; Egea, Pascal F.; Robles-Colmenares, Yaneth; O’Connell, Joseph D.; Stroud, Rhonda M.

doi:10.1371/journal.pbio.0000072

Cited by 272 publications

(269 citation statements)

References 32 publications

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“…Each bAQP0 monomer is Ϸ35 Å in diameter and contains one channel at its center that is oriented parallel to the 4-fold axis of the tetramer, as in other AQPs ( Fig. 1) (9,22,23). Note that four of the five 3D crystals and atomic-level structures of AQPs crystallize in different packing arrangements of the tetramers, as reflected in their different space groups.…”

Section: Resultsmentioning

confidence: 96%

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The channel architecture of aquaporin 0 at a 2.2-Å resolution

Harries

Akhavan

Miercke

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

252

274

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We determined the x-ray structure of bovine aquaporin 0 (AQP0) to a resolution of 2.2 Å. The structure of this eukaryotic, integral membrane protein suggests that the selectivity of AQP0 for water transport is based on the identity and location of signature amino acid residues that are hallmarks of the water-selective arm of the AQP family of proteins. Furthermore, the channel lumen is narrowed only by two, quasi-2-fold related tyrosine side chains that might account for reduced water conductance relative to other AQPs. The channel is functionally open to the passage of water because there are eight discreet water molecules within the channel. Comparison of this structure with the recent electron-diffraction structure of the junctional form of sheep AQP0 at pH 6.0 that was interpreted as closed shows no global change in the structure of AQP0 and only small changes in side-chain positions. We observed no structural change to the channel or the molecule as a whole at pH 10, which could be interpreted as the postulated pH-gating mechanism of AQP0-mediated water transport at pH >6.5. Contrary to the electron-diffraction structure, the comparison shows no evidence of channel gating induced by association of the extracellular domains of AQP0 at pH 6.0. Our structure aids the analysis of the interaction of the extracellular domains and the possibility of a cell-cell adhesion role for AQP0. In addition, our structure illustrates the basis for formation of certain types of cataracts that are the result of mutations.T he vertebrate ocular lens is a remarkably transparent and avascular tissue that acts basically as a syncytium of differentiated epithelial cells, called fiber cells. These cells are thin and highly elongated, and they are essentially a plasma membraneenclosed sack filled with transparent crystallin proteins. The lens is covered on the surface of its anterior hemisphere with a layer of simple squamous epithelial cells and an acellular capsule that encloses the entire lens. The lack of vascular-supply structures and any identifiable active transport systems in the fiber cell mass means that diffusional pathways are of paramount importance to the establishment and maintenance of lens homeostasis and transparency. The transparency of the lens, together with its ability to undergo dynamic shape changes during accommodation, provides for a clear and accurate image of the world to be projected onto the retina. The transparent nature of the lens is contingent on several crucial features that permit light to pass through with a minimum of light scattering. These features are (i) the maintenance of a highly ordered molecular structure of the crystallin proteins; (ii) terminally differentiated fiber cells containing very few organelles; and (iii) intracellular and intercellular spaces being kept smaller than the wavelength of ambient light (1-3).It is intriguing to understand the cellular and molecular basis for the maintenance of lens transparency, as well as the loss of lens transparency due to pathological and injur...

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Section: Resultsmentioning

confidence: 96%

“…Channel radius profile plot. Channel radius profiles of AQPs of known structure with corresponding structural elements are shown (22,23). The AQPZ ''A'' protomer was used for radius calculations for AQPZ.…”

Section: Resultsmentioning

confidence: 99%

The channel architecture of aquaporin 0 at a 2.2-Å resolution

Harries

Akhavan

Miercke

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

252

274

View full text Add to dashboard Cite

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“…There are five well-oriented waters in the AqpZ channel, forming a chain of water nearly the length of the channel, the waters form hydrogen-bond to side chains of several amino acids including amino acids in NPA motif and ar/R selectivity filter. Asn63 and Asn186 of the NPA motif form hydrogen bonds to the central water by their NH 2 moieties (Savage et al 2003). Another constriction is ar/R selectivity filter, it is formed on the extracytoplasmic side of the membrane by a spatial arrangement of aromatic and other amino acids (usually have an arginine residue).…”

Section: Structure Analysis Of Gjtipmentioning

confidence: 99%

“…The conservation of arginine, histidine and phenylalanine side chains at their respective locations within the constriction region in the known water channels is a strong indicator of channel water specificity. The selectivity filter of AqpZ is the narrowest point in it's water channel, it is formed by the side chains of Phe43, His174, Arg189 and the carbonyl of Thr183,the water in channel forms hydrogen-bond to the carbonyls of T183 (Savage et al 2003). AQGPs usually have Trp-GlaPhe-Arg, some AQGPs have His (Phe)-Ile(His)-Ala(Thr)-Val (Ma et al 2004), their selectivity filters usually are more hydrophobic than in AQPs.…”

Section: Structure Analysis Of Gjtipmentioning

confidence: 99%

Isolation of a fruit ripening-related tonoplast aquaporin (GjTIP) gene from Gardenia jasminoides

Gao

Guo

2013

Physiol Mol Biol Plants

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Aquaporins are membrane water channels that play critical roles in controlling the water content of cells and tissues. In this work, a full-length cDNA encoding putative aquaporins was isolated from Gardenia jasminoides fruit cDNA library. The GjTIP cDNA is 1188 bp, contains a predicted 774 bp open reading frame that encodes 257 amino acids. A phylogenetic analysis conducted with previously characterized aquaporins from other plant species indicates that the cDNA encode putative tonoplast aquaporins (TIPs), and proposed that GjTIP has a tendency to be a mixed function aquaporin similar to the TIP1s from Arabidopsis and Gossypium raimondii. A typical "hourglasses" three-dimensional model of GjTIP was built. The expression of the GjTIP transcripts at fruits during maturation was conducted by RT-PCR analysis. The data revealed that the transcript levels of GjTIP have increased during fruit maturation.

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“…5c), and from Escherichia coli the glycerol facilitator GlpF (PDB 1FX8) [22] (Fig. 5d) and water channel AqpZ (PDB 1RC2) [23] (Fig. 5e).…”

Section: D and 3d Crystal Structures Of Aquaporinsmentioning

confidence: 99%

Interactions of lipids with aquaporin-0 and other membrane proteins

Hite

Gonen

Walz

2007

Pflugers Arch - Eur J Physiol

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The structure of aquaporin-0 (AQP0) has recently been determined by electron crystallography of two-dimensional (2D) crystals and by x-ray crystallography of three-dimensional (3D) crystals. The electron crystallographic structure revealed nine lipids per AQP0 monomer, which form an almost complete bilayer. The lipids adopt a wide variety of conformations and tightly fill the space between adjacent AQP0 tetramers. The conformations of the lipid acyl chains appear to be determined not only by the protein surface but also by the acyl chains of adjacent lipid molecules. In the x-ray structure, the hydrophobic region of the protein is surrounded by a detergent micelle, with two ordered detergent molecules per AQP0 monomer. Despite the different environments, the electron crystallographic and x-ray structures of AQP0 are virtually identical, but they differ in the temperature factors of the atoms that either contact the lipids in the 2D crystals or are exposed to detergents in the 3D crystals. The temperature factors are higher in the x-ray structure, suggesting that the detergent-exposed AQP0 residues are less ordered than the corresponding ones contacting lipids in the 2D crystals. An examination of ordered detergent molecules in crystal structures of other aquaporins and of lipid molecules in 2D and 3D crystals of bacteriorhodopsin suggests that the increased conformational variability of detergent-exposed residues compared to lipid-contacting residues is a general feature.

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Architecture and Selectivity in Aquaporins: 2.5 Å X-Ray Structure of Aquaporin Z

Cited by 272 publications

References 32 publications

The channel architecture of aquaporin 0 at a 2.2-Å resolution

The channel architecture of aquaporin 0 at a 2.2-Å resolution

Isolation of a fruit ripening-related tonoplast aquaporin (GjTIP) gene from Gardenia jasminoides

Interactions of lipids with aquaporin-0 and other membrane proteins

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