SEQUENCE AND FUNCTIONAL EXPRESSION OF AN AMPHIBIAN WATER CHANNEL, FA-CHIP - A NEW MEMBER OF THE MIP FAMILY

A new member of the family of water channel proteins (aquaporin-CHIP) related to the major intrinsic protein (MIP) family is described. The cDNA coding for this amphibian CHIP vias cloned from frog (Rana escule nta) urinary bladder, a model for the kidney collecting duct, using a RT-PCR cloning strategy. The encoded protein, designated FA-CHIP (frog aquaporin-CHIP), shows 77.4%, 42.4% and 35.6% identity with the three proteins new referred to as the aquaporins of the MIP family, i.e., h uman CHIP28, WCH-CD and gamma-TIP, respectively. Xenopus leavis inject ed with FA-CHIP cRNA exhibited a marked increase of the osmotic water permeability.