Precursors of molecules related to mammalian opioid peptides in brain of a marine worm

Total mRNA were extracted from brain of Nereis diversicolor (Annelida, Polychaeta) and were translated in vitro or in ovo. The newly synthesized polypeptides were analyzed through electrophoresis of immunoprecipitated products or the Western blotting technique using polyclonal antibodies raised against mammalian dynorphin 1–17 and mammalian α‐neo‐endorphin. Among the products translated in vitro, only one class of polypeptide of 70 kDa was recognized by anti‐dynorphin 1–17 antibodies. Furthermore, some in ovo translated products as well as proteins extracted from brain of worms showed identical immunoreactivity. These polypeptides, 60–70 kDa, reacted with anti‐dynorphin 1–17 and anti α‐neo‐endorphin antibodies. These results suggest the existence of epitopes common to in ovo and in vitro translated products, to polypeptides extracted from the brain and to some mammalian opioid peptides of the prodynorphin family. We postulate the presence, in the brain of N. diversicolor, of precursors of peptides related to mammalian dynorphin 1–17 and α‐neo‐endorphin. Data reported in this investigation do not allow us to propose or even postulate the presence, in the brain of the worm, of one precursor molecule common to polypeptides related to mammalian dynorphin 1–17 and α‐neo‐endorphin. Furthermore, the Nereis precursor molecules exhibit a clear‐cut difference in molecular mass with the mammalian prodynorphin: 70 kDa versus 30 kDa.