A novel active pentapeptide from chicken brain identified by antibodies to FMRFamide.

The tetrapeptide Phe-Met-Arg-Phe-NH2 (FMRFamide) and peptides structurally related to it, have been isolated from molluscan ganglia. They have widespread actions on both invertebrate and vertebrate tissues and there is increasing evidence that they are an important group of invertebrate peptide neurotransmitters. It is of interest that the primary amino acid sequence of FMRFamide forms the C-terminal tetrapeptide of an enkephalin-like heptapeptide (Met-enkephalin-ArgPhe) isolated from bovine adrenal medulla and striatum. Antisera to FMRFamide have been shown to react in radioimmunoassay and immunohistochemistry with material in the central nervous system of various vertebrate species, but the identity of this material, and in particular its relationship to the opioid heptapeptide, remains uncertain. We have used antibodies specific for the C-terminus of FMRFamide in radioimmunoassays to monitor purification of the material in chicken brain. We describe here the sequence of one of the peptides obtained. It is a biologically active peptide which does not seem to be related to other known vertebrate neuropeptides.