Function
Aquaporins are channel producing proteins which regulate the flow of water across the cell membrane. The image on the left shows the protein, 6 molecules of glycerol and one of beta-octylglucoside.[1]
- Aquaporin-0 functions as water channel in lens fibers.
- Aquaporin-1 see details in Aquaporin-1.
- Aquaporin-2 function is to reabsorb water from urine in the kidney.
- Aquaporin-3 function is to promote glycerol permeability across cell membrane.
- Aquaporin-4 regulates water balance in the central nervous system.
- Aquaporin-5 is implicated in the forming of saliva, tears and pulmonary secretions.
- Aquaporin-Z is a major water channel in bacteria.
- Aquaglycerolporin (GLpf) is a water channel which can transport glycerol, polyalcohols, urea and other small solutes.
Disease
Mutations in aquaporin-2 cause diabitis insipidus. Mutations in aquaporin-0 in mice cause congenital cataracts. Aquaporin-4 is the primary autoimmune target of neuromyelitis optica.
Structural highlights
. The water transporting channel contains 2 restriction sites conferring an hourglass model to the channel. Two NPA motifs from opposite surfaces form one restriction. Another restriction is formed by a cluster of aromatic/arginine side chains which serves to weaken the hydrogen bonding between water molecules.
