MOLECULAR-CLONING OF CDNA FOR SAPECIN-B, AN ANTIBACTERIAL PROTEIN OF SARCOPHAGA, AND ITS DETECTION IN LARVAL BRAIN

A cDNA clone for sapecin B, an antibacterial protein of Sarcophaga, was isolated. This cDNA encoded a precursor protein of sapecin B consisting of a signal sequence (24 residues), prosegment (30 residues) and mature sapecin B (34 residues). Sapecin B was synthesized almost exclusively in the fat body when the larval body wall was injured, but the brain of naive larvae was also demonstrated to contain a significant amount of sapecin B. These findings suggested that sapecin B is a bifunctional protein.