Sequence of pedal peptide: a novel neuropeptide from the central nervous system of Aplysia

We report the identification of a novel neuropeptide from Aplysia nervous tissue. The peptide was termed Pedal peptide (Pep) because it was predominantly synthesized in the pedal ganglia. Pep was purified and sequenced from pooled extracts of pedal ganglia. The following sequence was proposed: Pro-Leu-Asp-Ser-Val-Tyr-Gly-Thr-His-Gly-Met-Ser-Gly-Phe-Ala. Enzymatic hydrolysis procedures indicated that Pep had a free carboxyl terminal. A peptide with the proposed sequence was synthesized and compared with the native peptide. Chromatographic properties of the 2 peptides under 3 different conditioned were compared and found to be identical. Electrophysiological responses to the 2 peptides were compared on an identified neuron in the abdominal ganglia and found to be qualitatively and quantitatively very similar. Both peptides produced net inward currents that were associated with a decrease in membrane conductance. The results from these 2 procedures confirmed that the proposed Pep sequence was correct. Quantitative measurements of the incorporation of 35S-methionine into Pep suggest that cell bodies that synthesize Pep were present predominantly in the pedal ganglia but should also be found in other central ganglia as well. Pep-like immunoreactive neurons are found predominantly in the pedal ganglia and less frequently in the other ganglia (Pearson and Lloyd, 1989). Quantitatively, Pep constitutes one of the predominant peptides in the nervous system of Aplysia. Pep does not appear to be a member of any other previously identified invertebrate or vertebrate peptide family.