IDENTIFICATION OF A NOVEL DUAL ANGIOTENSIN-II VASOPRESSIN RECEPTOR ONTHE BASIS OF MOLECULAR RECOGNITION THEORY

The molecular recognition theory suggests that binding sites of intera cting proteins, for example, peptide hormone and its receptor binding site, were originally encoded by and evolved from complementary strand s of genomic DNA. To test this theory, we screened a rat kidney comple mentary DNA library twice: first with the angiotensin II (All) followe d by the vasopressin (AVP) antisense oligonucleotide probe, expecting to isolate cDNA clones of the respective receptors. Surprisingly, the identical cDNA clone was isolated twice independently. Structural anal ysis revealed a single receptor polypeptide with seven predicted trans membrane regions, distinct All and AVP putative binding domains, a G(s ) protein-activation motif, and an internalization recognition sequenc e. Functional analysis revealed specific binding to both All and AVP a s well as All- and AVP-induced coupling to the adenylate cyclase secon d messenger system. Site-directed mutagenesis of the predicted AII bin ding domain obliterates All binding but preserves AVP binding. This co rroborates the dual nature of the receptor and provides direct molecul ar genetic evidence for the molecular recognition theory.