Rapid gating and anion permeability of an intracellular aquaporin

摘要: Aquaporin (AQP) water-channel proteins are freely permeated by water but not ions or charged solutes. Although mammalian aquaporins were believed to be located in plasma membranes, rat AQP6 is restricted intracellular vesicles renal epithelia. Here we show that functionally distinct from other known aquaporins. When expressed Xenopus laevis oocytes, exhibits low basal permeability; however, when treated with the channel inhibitor, Hg2+, permeability of oocytes rapidly rises up tenfold and accompanied ion conductance. colocalizes H+-ATPase acid-secreting alpha-intercalated cells collecting duct. At pH less than 5.5, anion conductance reversibly activated oocytes. Site-directed mutation lysine glutamate at position 72 cytoplasmic mouth pore changes cation/anion selectivity, leaves activation intact. Our results demonstrate unusual biophysical properties an aquaporin, indicate anion-channel function may now explored a protein structure.