Purification and chemical characterization of caudodorsal cell hormone-II from the egg-laying controlling caudodorsal cells of Lymnaea stagnalis.

Caudodorsal cell hormone-I (CDCH-I), a 36 amino acid peptide synthesized by the caudodorsal cells (CDCs), is one of the major neuropeptides present in the cerebral ganglia of the freshwater snail, Lymnaea stagnalis. This peptide induces ovulation and egg-mass formation, and, in addition, acts on neuronal circuits involved in the control of overt egg-laying behavior. cDNA cloning studies revealed that there is a CDCH gene family comprising two genes coding for CDCH-I and the related yet distinct CDCH-II, respectively. In the present study, using sequential high performance gel permeation and reversed phase high performance liquid chromatography, we have isolated and sequenced the peptide CDCH-II. This neuropeptide has the following sequence: Ser-Ile-Thr-Asn-Asp-Leu-Arg-Ala-Ile-Ala-Asp-Ser-Tyr-Leu-Tyr-Asp-Gln-His- Lys-Leu - Arg-Glu-Gln-Gln-Glu-Glu-Asn-Leu-Arg-Arg-Arg-Phe-Tyr-Glu-Leu-Ser-Leu-Arg- Pro-Tyr - Pro-Asp-Asn-Leu. The sequence differs from those predicted by the cDNA sequence encoding preproCDCH-II at two positions, suggesting the polymorphism of CDCH-II exists in L. stagnalis.