Characterization of a cDNA encoding a precursor polypeptide of a D-amino acid-containing peptide, achatin-I and localized expression of the achatin-Iand fulicin genes

Achatin-I and fulicin, isolated from the ganglia and atria of the giant lan d snail Achatina fulica, are a tetrapeptide and pentapeptide containing a D -Phe and D-Asn at position 2, respectively. We succeeded in cloning a cDNA encoding a precursor of achatin-I from the Achatina ganglia, revealing that the D-Phe present in achatin-I is coded by a common L-Phe codon, TTT or TT C. The deduced polypeptide was found to comprise seven repeats of the achat in sequence GFAD and one analog GFGD flanked on both sides by the typical e ndoproteolytic site KR. Northern blot analysis of transcripts and Southern blot analysis of reverse transcription (RT)-PCR products demonstrated that achatin-I mRNA was localized in the subesophageal ganglia, whereas expressi on of fulicin mRNA was detected in the atrium as well as in the subesophage al ganglia. Furthermore, localization of the achatin gene transcript in the right and left pedal ganglia compartments was shown by in situ hybridizati on on sections of subesophageal ganglia, whereas the fulicin transcript was observed in the right and left parietal ganglia. These data suggested that achatin-I plays an essential role in the regulation of the heart as a neur otransmitter or neurohormone through production in the pedal ganglia and tr ansport to the atrium, whereas fulicin serves not only as a neurotransmitte r or neurohormone but also as a novel atrial hormone.