High affinity binding of the mastoparans by calmodulin

Calmodulin exhibits high affinity, calcium-dependent binding of the mastoparans — a group of cytoactive tetradecapeptides. The dissociation constants for the peptide-calmodulin complexes determined in 0.20 N KCl, 1.0 mM CaCl₂, pH 7.3 are ～0.3 nM for mastoparan, ～0.9 nM for mastoparan X, and ～3.5 nM for $\text{Polistes}$ mastoparan. The dissociation constant for the mastoparan-calmodulin complex is the smallest known for any calmodulin binding protein or peptide, suggesting that some type of peptide-calmodulin interaction could be physiologically significant.