Unique to AQP0 without significant homology to any other AQPs. It has significant homology with bovine (94%), rat/mouse (88%) and frog (70%) AQP0
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 "aquaporin". Over the last decade, genes for several members of aquaporin family have been cloned, expressed, and their distribution studied in many tissues. AQP0 or MIP26 (major intrinsic protein 26kD), and Aquaporin-1 (AQP1, purified from red cells) also called CHIP-28 (channel forming integral protein, 28kD; 268aa; gene locus 7p14) has been the foundation of the growing family of aquaporin. The lens specific AQP0 represents up to 80% of total lens membrane protein. Defects in MIP26 are cause of autosomal dominant cataract. The cataract Fraser mutation (CAT-FR or Shriveled) is a transposon-induced splicing error that substitutes a long terminal repeat sequence for the c-terminus of MIP. The lens opacity mutation (LOP) is an amino acid substitution that inhibits targeting of MIP to the cell membrane.
Human AQP0 is a 263 amino acid transmembrane protein belonging to the MIP family. AQP families of proteins are predicted to contain six transmembrane domains. The N and C-terminus are predicted to be cytoplasmic. A 17aa synthetic peptide within the carboxy terminal domain of human AQP0 (1) was selected for antibody production. This domain is predicted to be cytoplasmic. Antibodies were generated in chicken. Antibodies have been affinity purified using the control peptide-Sepharose.
