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aquaporin-3; AQP-3 (AQP3)
Function:
- forms a water-specific channel that provide kidney medullary collecting duct with high permeability to water, permitting water to move in the direction of an osmotic gradient
- may function as a water & urea exit mechanism in antidiuresis in collecting duct cells
- slightly permeable to urea & glycerol
- may play an important role in gastrointestinal tract water transport & in glycerol metabolism (putative)
Structure:
- aquaporins contain two tandem repeats each containing 3 membrane-spanning domains & a pore-forming loop with the signature motif Asn-Pro-Ala (NPA)
- belongs to the MIP/aquaporin (TC 1.A.8) family
Compartment:
- basolateral cell membrane in collecting ducts of kidney
Alternative splicing: named isoforms=2
Expression:
- widely expressed in epithelial cells of kidney (collecting ducts) & airways, in keratinocytes, immature dendritic cells & erythrocytes
- isoform 2 is not detectable in erythrocytes at the protein level
Polymorphism:
- AQP3 is responsible for the GIL blood group system
- polymorphism at the 5'-splice donor site of intron 5, leading to exon 5 skipping & premature termination of translation
- isoform 2 is detected in GIL-negative individuals that lack functional AQP3
General
aquaporin
glycoprotein
transmembrane 6 protein
Properties
SIZE: entity length = 292 aa
MW = 32 kD
COMPARTMENT: plasma membrane
MOTIF: cytoplasmic domain {1-28}
transmembrane domain {29-49}
exoplasmic loop {50-53}
transmembrane domain {54-74}
cytoplasmic loop {75-109}
MOTIF: peptide motif {83-85}
transmembrane domain {110-130}
exoplasmic loop {131-157}
MOTIF: N-glycosylation site {N141}
transmembrane domain {158-178}
cytoplasmic loop {179-188}
transmembrane domain {189-209}
exoplasmic loop {210-244}
MOTIF: peptide motif {215-217}
transmembrane domain {245-265}
cytoplasmic domain {266-292}
Database Correlations
OMIM correlations
UniProt Q92482
Pfam PF00230
Entrez Gene 360
Kegg hsa:360
References
- UniProt :accession Q92482
- OMIM :accession 600170
- dbRBC/BGMUT; Note: Blood group antigen gene mutation database
http://www.ncbi.nlm.nih.gov/gv/mhc/xslcgi.cgi?cmd=bgmut/systems_info&system=gil
- SeattleSNPs
http://pga.gs.washington.edu/data/aqp3/