Effects of the hinge region of cecropin A(1-8)-magainin 2(1-12), a synthetic antimicrobial peptide, on liposomes, bacterial and tumor cells

A 20-residue hybrid peptide (CA(1-8)-MA(1-12): KWKLFKKTGIGKFLHSAKKF-NH2) in corporating 1-8 residues of cecropin A (CA) and 1-12 residues of magainin 2 (MA) has potent antibiotic activity without hemolytic activity. In order t o investigate the effects of the flexible hinge sequence, Gly-Ile-Gly of CA (1-8)-MA(1-12) (CA-MA) on antibiotic activity, CA-MA and its three analogue s, CA-MA1, CA-MA2 and CA-MA3 were synthesized. The Gly-Ile-Gly sequence of CA-MA was deleted in CA-MA1 and replaced with Pro and Gly-Pro-Gly in CA-MA2 and CA-MA3, respectively. CA-MA1 and CA-MA3 caused a significant decrease in the bactericidal rate against Escherichia coli and Bacillus subtilis and the tumoricidal activity against four different tumor cells, and the PC/PS (4:1, w/w) vesicle-aggregating and disrupting activities. However, CA-MA2 showed a similar bactericidal rate and antitumor, vesicle-aggregating and d isrupting activities, as compared with CA-MA. These results suggested that the flexibility or beta-turn induced by Gly-Ile-Gly or Pro in the central p art of CA-MA may be important in the electrostatic interaction of the catio nic short alpha-helical region in the N-terminus with the cell membrane sur face and the hydrophobic interaction of amphipathic alpha-helical region in the C-terminus with the hydrophobic acyl chains in the cell membrane. CA-M A3 exhibited lower activity in antibacterial, antitumor, and vesicle-aggreg ating and disrupting activities than CA-MA and CA-MA2. This result suggeste d that the excessive beta-turn structure by Gly-Pro-Gly in CA-MA3 seems to interrupt the ion channel/pore formation on the lipid bilayer. It was concl uded that the appropriate flexibility or beta-turn structure provided by th e central hinge is responsible for the effective antibiotic activity of the antimicrobial peptides with the helix-hinge-helix structure. (C) 2000 Else vier Science B.V. All rights reserved.