Aquaporin-2 (AQP-2)(Aquaporin-CD)(AQP-CD)(Water channel protein for renal collecting duct)(ADH water channel)(Collecting duct water channel protein)(WCH-CD); Forms a water-specific channel that provides the plasma membranes of renal collecting duct with high permeability to water, thereby permitting water to move in the direction of an osmotic gradient (271 aa)