Neuropeptides Gly-Asp-Pro-Phe-Leu-Arg-Phe-amide (GDPFLRFamide) and Ser-Asp-Pro-Phe-Leu-Arg-Phe-amide (SDPFLRFamide) Are Encoded by an Exon 3’ to Phe-Met-Arg-Phe- NH, (FMRFamide) in the Snail Lymnaea stagnalis

Biochemical analysis has shown the pond snail Lymnaea stagnalis to contain 2 main classes of Phe-Met-Arg-Phe-NH, (FMRFamide)-like neuropeptides: the tetrapeptides FMRFamide and Phe-Leu-Arg-Phe-NH, (FLRFamide), and the heptapeptides Gly-Asp-Pro-Phe-Leu-Arg-Phe-NH, (GDPFLRFamide) and Ser-Asp-Pro-Phe-Leu-Arg-Phe-NH, (SDPFFRFamide). By genomic mapping and DNA sequencing, we show here that the GDP/SDPFLRFamide coding region lies 3’ to the FMRFamide coding region. The absence of an initiating start methionine and the presence of good-concensus 3’ and 5’ splice sites suggests that the GDP/SDPFLRFamide coding region makes up 1 exon of a larger gene. In addition to 7 copies of GDPFLRFamide and 6 copies of SDPFLRFamide, the exon encoding the heptapeptides also encodes 3 novel peptides, Glu-Phe-Phe-Pro-Leu-NH, (EFFPLamide), Ser-AspPro-Tyr-Leu-Phe-Arg-NH, (SDPYLFRamide), and Ser-AspPro-Phe-Phe-Arg-Phe-NH, (SDPFFRFamide). In contrast to the tetrapeptide FMRFamide precursor protein, the GDP/ SDPFLRFamide peptides are encoded contiguously, being separated only by single basic amino acids.