Two introns define functional domains of a neuropeptide precursor in Aplysia

Biologically active peptides are synthesized as parts of precursor proteins which are proteolytically processed to generate active molecules. The structure of the gene encoding peptides expressed in Aplysia neurons R3-14 suggests that two intervening sequences split the transcript into functional domains. The first exon encodes the 5' untranslated region, the second exon the signal sequence and the bulk of the negative charge of the precursor protein while the third exon encodes the remainder of the precursor and the 3' untranslated region.