Egg-laying hormone peptides in the Aplysiidae family

The neuropeptidergic bag cells of the marine mollusc Aplysia californica ar e involved in the egg-laying behavior of the animal, These neurosecretory c ells synthesize an egg-laying hormone (ELH) precursor protein, yielding mul tiple bioactive peptides, including ELH, several bag cell peptides (BCP) an d acidic peptide (AP), While immunohistochemical studies have involved a nu mber of species, homologous peptides have been biochemically characterized in relatively few Aplysiidae species. In this study, a combination of matri x-assisted laser desorption/ionization time-of-flight mass spectrometry (MS ) and electrospray ionization Fourier transform ion cyclotron resonance MS is used to characterize and compare the ELH peptides from related opisthobr anch molluscs including Aplysia vaccaria and Phyllaplysia taylori, The pept ide profiles of bag cells from these two Aplysiidae species are similar to that of A, californica bag cells. In an effort to characterize further seve ral of these peptides, peptides from multiple groups of cells of each speci es were extracted, and microbore liquid chromatography was used to separate and isolate them. Several MS-based sequencing approaches are applied to ob tain the primary structures of bag cell peptides and ELH, Our studies revea l that alpha-BCPs are :100 % conserved across all species studied. In addit ion, the complete sequences of epsilon-BCP and ELH of A. vaccaria were dete rmined. They show a high degree of homology to their counterparts in A, cal ifornica, with only a few amino acid residue substitutions.