AT4 RECEPTOR-BINDING CHARACTERISTICS - D-AMINO-ACID-SUBSTITUTED AND GLYCINE-SUBSTITUTED PEPTIDES

The ability of angiotensin IV (AIV) analogs to compete for [I-125]AIV binding in heat-treated bovine adrenal membranes was examined. Angiotensin IV displayed a K(i) of 2.63 +/- 0.12 nM. Peptides containing mono-substitutions with glycine or the corresponding D-amino acid in positions one, two, or three possessed K(i)s greater than 100 nM. Conversely, substitutions at positions four, five, and six produced peptides with K(i)s less than 8 nM. These data suggest that the N-terminal domains of the AIV peptide are critical for receptor binding, while the C-terminal domains play a less decisive role in receptor specificity.