Binding and activation regions of the decapeptide PDVDHVFLRFamide (SchistoFLRFamide).

In the oviduct of Locusta migratoria, a FMRFamide-related peptide, PDVDHVFLRFamide (SchistoFLRFamide) acts as a neuromodulator, inhibiting spontaneous and induced muscle contraction. In this study, we have used N-terminal truncated peptides to show that PDVDHVFLRFamide has separated binding and activation regions. VFLRFamide is the minimum sequence required for binding, whereas HVFLRFamide is the minimum sequence for inhibitory biological activity. Thus the His residue, which does not contribute to binding, is a critical amino acid for the activation of the receptor. The N-terminal PDVD appears to play little or no role in either binding or activation. VFLRFamide, which binds to the receptor but yields no inhibitory biological activity, is a strong antagonist of PDVDHVFLRFamide.