Structural highlights
Function
AQP4_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 PubMed
Phosphorylation of Ser180 in cytoplasmic loop D has been shown to reduce the water permeability of aquaporin (AQP) 4, the predominant water channel in the brain. However, when the structure of the S180D mutant (AQP4M23S180D), which was generated to mimic phosphorylated Ser180, was determined to 2.8 A resolution using electron diffraction patterns, it showed no significant differences from the structure of the wild-type channel. High-resolution density maps usually do not resolve protein regions that are only partially ordered, but these can sometimes be seen in lower-resolution density maps calculated from electron micrographs. We therefore used images of two-dimensional crystals and determined the structure of AQP4M23S180D at 10 A resolution. The features of the 10-A density map are consistent with those of the previously determined atomic model; in particular, there were no indications of any obstruction near the cytoplasmic pore entrance. In addition, water conductance measurements, both in vitro and in vivo, show the same water permeability for wild-type and mutant AQP4M23, suggesting that the S180D mutation neither reduces water conduction through a conformational change nor reduces water conduction by interacting with a protein that would obstruct the cytoplasmic channel entrance. Finally, the 10-A map shows a cytoplasmic density in between four adjacent tetramers that most likely represents the association of four N termini. This finding supports the critical role of the N terminus of AQP4 in the stabilization of orthogonal arrays, as well as their interference through lipid modification of cysteine residues in the longer N-terminal isoform.
Influence of the cytoplasmic domains of aquaporin-4 on water conduction and array formation.,Mitsuma T, Tani K, Hiroaki Y, Kamegawa A, Suzuki H, Hibino H, Kurachi Y, Fujiyoshi Y J Mol Biol. 2010 Oct 1;402(4):669-81. Epub 2010 Aug 13. PMID:20709083[1]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
See Also
References
- ↑ Mitsuma T, Tani K, Hiroaki Y, Kamegawa A, Suzuki H, Hibino H, Kurachi Y, Fujiyoshi Y. Influence of the cytoplasmic domains of aquaporin-4 on water conduction and array formation. J Mol Biol. 2010 Oct 1;402(4):669-81. Epub 2010 Aug 13. PMID:20709083 doi:10.1016/j.jmb.2010.07.060
