Perturbation of the lipid bilayer of model membranes by synthetic signal peptides.

The interaction of synthetic peptides corresponding to the signal sequences of Escherichia coli alkaline phosphatase: Lys-Gln-Ser-Thr-Ile-Ala-Leu-Ala-Leu-Leu-Pro-Leu-Leu-Phe-Thr-Pro-Val-Thr- Lys-Ala - OCH3, chicken lysozyme: Met-Lys-Ser-Leu-Leu-Ile-Leu-Val-Leu-Cys(Bzl)-Phe-Leu-Pro-Leu- Ala-Ala-Leu-Gly-OCH2-C6H5 and variant of the chicken lysozyme signal sequence with a charged residue in the hydrophobic region: Lys-Leu-Leu-Ile-Ala-Leu-Val-Leu-Lys-Phe-Leu-Pro-Leu-Ala-Ala- Leu-Gly-OCH3 with model membranes of brain phosphatidylserine (PS) and egg phosphatidylcholine (PC) have been investigated by 90 degrees light scattering and fluorescence spectroscopy. Our results indicate that the association of signal peptides with model membranes results in extensive perturbation of the lipid bilayer so as to cause fusion of PS vesicles and aggregation of PC vesicles. The vesicles are also rendered permeable to hydrophilic molecules like carboxyfluorescein. The variant peptide with the lysine residue in the hydrophobic region also has the ability to perturb lipid bilayers of model membranes.