Fusion of liposomes due to transient and lasting perturbation induced by synthetic amphiphilic peptides.

The membrane-fusion activities of amphiphilic peptides of H-(Leu-Aib-Lys-Aib-Aib-Lys-Aib)n-Ala-N(C18H37)2 (n = 1, P7D and n = 3, P21D) immobilized on liposome were investigated. P7D, which takes a random conformation, induced fusion of DPPC SUV, but P7D immobilized on the DPPC SUV did not show the fusion activity. On the other hand, P21D showed a high activity of membrane fusion either in the free peptide or in the immobilized state. CF-Leakage experiments revealed that the peptides caused a transient perturbation of the membrane structure on binding to the membrane. A lasting and steady perturbation was also caused by P21D embedded in the membrane, which was indicated by EU3+ permeation through the membrane. This type of membrane perturbation was very slight in the case of P7D embedded in the membrane. A conclusion was reached that the different activities in the membrane fusion are based on the transient perturbation in the membrane at the peptide binding to the membrane surface as well as the steady perturbation caused by the peptide embedded in the membrane.