Purification of an angiotensin II binding protein by using antibodies to a peptide encoded by angiotensin II complementary RNA.

We have generated a monospecific antibody to a synthetic peptide encoded by an RNA complementary to the mRNA for angiotensin II (AII) and determined whether this antibody recognizes the AII receptor. We demonstrate that the antibody competes specifically with 125I-labeled AII for the same binding site on rat adrenal membranes. Furthermore, we show that this antibody inhibits the secretion of aldosterone from cultured rat adrenal cells, suggesting that the antibody recognizes the biologically relevant AII receptor. Finally, we demonstrate that antibody to the complementary peptide can be used to immunoaffinity-purify a protein of Mr 66,000 that specifically binds radiolabeled AII.