Amiloride Binding Protein 1 (ABP1)

On the basis of its primary structure, the amiloride-binding protein (EC 1.4.3.6) is 713 amino acids long, with a 19-amino acid signal peptide. Expressed in cultured cells, the mRNA yields a glycoprotein that binds amiloride and amiloride analogs with affinities similar to the amiloride receptor associated with the apical Na+ channel in pig kidney membranes and is immunoprecipitated with monoclonal antibodies raised against pig kidney amiloride-binding protein. Barbry et al. (1990) pointed out that amiloride-sensitive Na+ channels are also present in airway epithelia, where they play an important role in fluid secretion. Amiloride inhibits the excessive absorption of Na+ and liquid that takes place in airway epithelia of patients with cystic fibrosis, and amiloride aerosol therapy has been tried for the treatment of lung disease in CF.