Antibacterial activities of peptides designed as hybrids of antimicrobial peptides

Hybrid peptides (HP-MA, HP-ME), each of 20 residues and incorporating 2-9 residues of Helicobacter pylori ribosomal protein L1 (HP) and 1-12 residues of magainin 2 and melittin, were designed. The antibiotic activities of these peptides were evaluated using bacterial, tumor and human erythrocyte cells. HP-MA had a stronger antibacterial activity against Gram-positive bacteria and Gram-negative bacteria than HP (2-20) and magainin 2, and HP-ME was similar to melittin. None of the hybrids had anti-tumor or hemolytic activity. These peptides were further investigated using an artificial liposomal vesicle and 1,6-diphenyl-1,3,5-hexatriene as a membrane probe, and confirmed to have similar antibacterial activities. The antibacterial effect of these hybrids is probably caused by their ability to damage the bacterial plasma membrane. Additional circular dichroism spectra suggested that the alpha-helical structure of these peptides plays an important role in their antibiotic effect but that alpha-helical property is less connected with the enhanced antibiotic activity.