Investigation of the structure/activity relationship of human calcitonin gene-related peptide (CGRP)

The biological activities of calcitonin gene-related peptide (CGRP) enzymic digest fragments, chemically modified products and β-CGRP have been compared to that of intact α-CGRP on rat isolated paired atria. Tryptic and chymotryptic digests both produced inactive fragments. Acetylation of the N-terminal amino acid (Alanine) or either of Lys 24 or Lys 35, resulted in reduced, but measurable, biological activity. Destruction of the disulphide bridge between Cys 2 and Cys 7 abolished biological activity. Substitution of several amino acids, Asp 3, Val 22 and Asn 25, with Asn, Met and Ser respectively (β-CGRP), produced a peptide with similar biological activity to α-CGRP.