Water is a critical component of all living cells. Interestingly, tissue membranes show a great degree of water permeability. Mammalian red cells, renal proximal tubules, and descending thin limb of Henle are extraordinarily permeable to water. Water crosses hydrophobic plasma membranes either by simple diffusion or through a facilitative transport mechanism mediated by special protein aquaporins. Aquaporin 0 or MIP26 (major intrinsic protein 26kD), and Aquaporin 1 has been the foundation of the growing family of aquaporins. The lens specific Aquaporin 0 represents up to 80% of total lens membrane protein. Defects in Aquaporin 0 are a cause of autosomal recessive congenital cataract. The lens opacity mutation (LOP) is an AA substitution that inhibits targeting of MIP to the cell membrane. Human Aquaporin 0 is a 263 amino acid transmembrane protein belonging to the MIP family. Aquaporin families of proteins are predicted to contain six transmembrane domains. The N and C terminus are predicted to be cytoplasmic.
Function:
Water channel. May be responsible for regulating the osmolarity of the lens. Interactions between homotetramers from adjoining membranes may stabilize cell junctions in the eye lens core.
Subunit:
Homotetramer. Homooctamer formed by head-to-head interaction between homotetramers from adjoining membranes. During early stages of lens development, interacts through its SLCterminal region with Cx56 and GJA8/Cx45.6.
Subcellular Location:
Cell membrane; Multi-pass membrane protein. Cell junction, gap junction.
Tissue Specificity:
Major component of lens fiber gap junctions.
Similarity:
Contains 1 homeobox DNA-binding domain.
Contains 2 LIM zinc-binding domains.
SWISS:
P30301
Gene ID:
4284
Database links:
Entrez Gene: 4284 Human
Entrez Gene: 17339 Mouse
Entrez Gene: 2596 Rat
Omim: 154050 Human
SwissProt: P30301 Human
SwissProt: P5236 Mouse
SwissProt: P09011 Rat
Unigene: 574026 Human
Unigene: 31625 Mouse
Unigene: 396469 Mouse
Unigene: 23532 Rat
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