Primary Structure of a New Neuropeptide, Cerebral Peptide 2, Purified from Cerebral Ganglia of Aplysia

We report the purification and characterization of a novel neuropeptide from Aplysia nervous tissue. The peptide was termed cerebral peptide 2 (CP2) because it was the larger of two peptides predominantly synthesized in the cerebral ganglia and transported to other regions of the central nervous system. The purification of CP2 from extracts of cerebral ganglia using three sequential modes of high-pressure liquid chromatography (HPLC) was followed using the [35S]methionine-labeled peptide obtained from transport experiments. The primary structure of CP2 was determined by automated Edman degradation of native CP2 and its proteolytic fragments in conjunction with mass spectrometry. CP2 is a 41 amino acid peptide with an amidated carboxyl terminal. A peptide with the proposed sequence of CP2 was synthetized and compared by HPLC with the native peptide. Chromatographic properties of the synthetic and native peptide labeled in vivo were found to be identical. CP2 does not appear to be a member of any previously identified peptide family.