Journal of Neuroscience, Vol 9, 312-317, Copyright © 1989 by Society for Neuroscience
Sequence of pedal peptide: a novel neuropeptide from the central nervous system of Aplysia
PE Lloyd and CM Connolly
Department of Pharmacological and Physiological Sciences, University of Chicago, Illinois 60637.
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.