Isolation of four novel neuropeptides, the hydra-RFamides I-IV, from Hydra magnipapillata.

Using a radioimmunoassay for the sequence Arg-Phe-NH2 (RFamide), we have isolated four novel peptides from extracts of Hydra magnipapillata: <Glu-Trp-Leu-Gly-Gly-Arg-Phe-NH2 (Hydra-RFamide I), <Glu-Trp-Phe-Asn-Gly-Arg-Phe-NH2 (Hydra-RFamide II), Lys-Pro-His-Leu-Arg-Gly-Arg-Phe-NH2 (Hydra-RFamide III) and His-Leu-Arg-Gly-Arg-Phe-NH2 (Hydra-RFamide IV). The Hydra-RFamides I-IV are neuropeptides. They form a peptide family with other known neuropeptides from hydromedusae, sea anemones and sea pansies.