Cardioactive neuropeptide Phe-Met-Arg-Phe-NH₂ (FMRFamide) and novel related peptides are encoded in multiple copies by a single gene in the snail Lymnaea stagnalis

The neuropeptide Phe-Met-Arg-Phe-NH₂ (FMRFamide) is a potent cardioactive neuropeptide in Lymnaea stagnalis. Isolation and sequencing of 2 cDNAs and a genomic clone shows that a single gene encodes a precursor protein which contains 9 copies of the FMRFamide peptide, 2 copies of the related peptide Phe-Leu-Arg-Phe-NH₂ (FLRFamide), and single copies of the putative pentapeptides Gln-Phe-Tyr-Arg-Ile-NH₂ (EFLRIamide). The gene is transcribed in the CNS and gives rise to a single RNA of 1.7 kb in size. The organization of the Lymnaea gene is significant with respect to the evolution of FMRFamide and related peptides in other organisms.