Purification, sequence and antibacterial activity of two novel sapecin homologues from Sarcophaga embryonic cells: similarity of sapecin B to charybdotoxin.

Two sapecin homologues were purified from the culture medium of NIH-Sape-4, an embryonic cell line of Sarcophaga peregrina (flesh fly). These homologues contained six cysteine residues with exactly the same disulphide pairings as those in sapecin. The amino acid sequence of one of them, sapecin C, was also very similar to that of sapecin. The other homologue, sapecin B, was less similar to sapecin but showed significant similarity to charybdotoxin, an inhibitor of K+ channels isolated from a scorpion venom. Like sapecin, these homologues repressed the growth of various Gram-positive bacteria.