Adaptation of a membrane-active peptide to heterogeneous environment. II. The role of mosaic nature of the membrane surface.

In the first article of this series we demonstrated the importance of specific intrapeptide interactions and peptide-lipid contacts for the membrane binding of penetratin (pAntp). Here in focus was detailed characterization of spatial hydrophobic/hydrophilic properties of the bilayer surface and their influence on the binding mode of pAntp. From the hydrophobicity point of view, the solvent-accessible surfaces of lipid bilayers possess a distinctly "mosaic" character. This correlates well with the occurrence of dynamic clusters of hydrophobic surface area formed by hydrocarbon tails of phospholipids exposed on the interface. Such mosaic patterns are specific for lipid bilayers of particular composition. In an anionic membrane, they determine initial stages of pAntp adsorption, which strongly depends on the "complementarity" between polarity properties of the peptide and its local interfacial environment. If high complementarity is established, then pAntp penetrates deeply into the membrane without significant destabilization of its initial secondary structure. Alternatively, partial unfolding of pAntp takes place in order to compensate unfavorable peptide-membrane interactions upon embedding. Such effects explain complicated behavior of membrane-active peptides, especially if the target membrane surface is of distinctly mosaic nature, depending on the microscopic properties of the water-lipid interface, pAntp is capable of adopting different pathways to exercise its biological activity.