Effect of dimerized melittin on gastric cancer cells and antibacterial activity.

Melittin is the peptide toxin found in bee venom and is effective against cancer cells. To enhance its activity, a branched dimeric form of melittin was designed. The monomeric form of the peptide was more cytotoxic against gastric cancer cells at low concentrations (1-5 μM) than the dimer form, while the cytotoxic effect was comparable at higher concentrations (10 μM). Confocal microscopy showed that both the monomer and dimer forms of melittin with fluorescent label at the C terminus penetrated the cytoplasm and localized at the cell nucleus and disrupted the cell membrane. The results indicated that both peptides localized in the nucleus and no significant difference in penetration was observed between monomer and dimer of melittin. Although the C and N termini are important for melittin activity, using C terminus for dimerization of the peptide resulted in similar activity for the monomer and dimer against bacteria and gastric cancer cells.