Title: Aquaporins
Literature References: Group of integral membrane proteins that function as molecular water channels to facilitate osmotic movement of water across the plasma membrane. Found in plant and animal cells characterized as having high osmotic water permeability. Part of the MIP family of channel proteins, typified by the major intrinsic protein of the eye, that are responsible for the permeability of ions and small molecules. Homologs exhibit ~40% sequence identity. Structure consists of six transmembrane domains with 5 connecting loops; the water pore is thought to be formed by the juxtaposition of 2 highly conserved Asn-Pro-Ala (NPA) sequences within the lipid bilayer. Isoln of aquaporin-1 from human erythrocytes and renal tubules: B. M. Denker et al., J. Biol. Chem. 263, 15634 (1988). Cloning and sequence homology with MIP family: G. M. Preston, P. Agre, Proc. Natl. Acad. Sci. USA 88, 11110 (1991). Identification of function as membrane water channel: G. M. Preston et al., Science 256, 385 (1992). Nomenclature: P. Agre et al., Am. J. Physiol. 265, F461 (1993). Molecular structure: J. S. Jung et al., J. Biol. Chem. 269, 14648 (1994). Review of structure and tissue distribution: C. H. van Os et al., Biochim. Biophys. Acta 1197, 291-309 (1994); M. J. Chrispeels, P. Agre, Trends Biochem. Sci. 19, 421-425 (1994). Review of aquaporins in plants: M. J. Chrispeels, C. Maurel, Plant Physiol. 105, 9-13 (1994). Review of role in renal water transport: A. F. van Lieburg et al., Pediatr. Nephrol. 9, 228-234 (1995); of model for water permeation: T. Zeuthen, Trends Biochem. Sci. 26, 77-79 (2001); of function and physiology in the kidney: S. Nielsen et al., Physiol. Rev. 82, 205-244 (2002).
Derivative Type: Aquaporin-1
Additional Names: AQP1; CHIP28; AQP-CHIP; aquaporin-CHIP; channel forming integral protein
Literature References: 269 amino acid residues; mol wt 28 kDa. Constitutes 2.4% of the plasma membrane protein in red blood cells; also found in renal proximal tubules and in other water-permeable epithelia.
Derivative Type: Aquaporin-2
Additional Names: AQP2; AQP-CD; WCH-CD; water channel of collecting duct
Literature References: 271 amino acids; mol wt 29 kDa. Vasopressin-regulated water channel in the kidney; has a primary role in concentrating the urine.
Derivative Type: g-TIP
Additional Names: g-Tonoplast intrinsic protein; AQP.At1
Literature References: Found in plant vacuolar membrane (tonoplast); facilitates rapid exchange of water between the vacuole and the cytoplasm.
Arabinose Arabitol Arachidic Acid Arachidonic Acid Aramite?

Crystallographic structure of aquaporin 1 (AQP1) PDB 1j4n
Symbol Aquaporin
Pfam PF00230
InterPro IPR000425
SCOP 1fx8
TCDB 1.A.8

Aquaporins are integral membrane proteins from a larger family of major intrinsic proteins (MIP) that form pores in the membrane of biological cells.[1]

Genetic defects involving aquaporin genes have been associated with several human diseases.[2][3] The 2003 Nobel Prize in Chemistry was awarded jointly to Peter Agre for the discovery of aquaporins,[4] and Roderick MacKinnon for his work on the structure and mechanism of potassium channels.[5] The plasma membranes of a variety of different animal and plant cells contain aquaporins through which water can flow more rapidly inside the cell than by diffusing through the phospholipid bilayer.[6]