1.D.164. The Cell-penetrating Amphipathic Peptide, Pep-1 (Pep-1) Family
Pep-1 delivers proteins and peptides into mammalian cells (Deshayes et al. 2004). It is an amphipathic peptide of 21 residues, which was designed on the basis of a protein-interacting domain associated with a nuclear localization sequence, separated by a linker. This peptide carrier constitutes a tool for the delivery of active proteins and peptides, both in cultured cells and in vivo, without requiring covalent coupling. Deshayes et al. 2004 examined the conformational states of Pep-1 in its free form and complexed with a cargo peptide and investigated their ability to interact with phospholipids and the structural consequences of these interactions. From the conformational point of view, Pep-1 behaves differently from other similarly designed cell-penetrating peptides. CD analysis revealed a transition from a nonstructured to a helical conformation upon increase of the concentration. Determination of the structure by NMR showed that in water, its alpha-helical domain extends from residues 4-13. CD and FTIR indicated that Pep-1 adopts a helical conformation in the presence of phospholipids. Adsorption measurements performed at the air-water interface were consistent with the helical form. Pep-1 does not undergo conformational changes upon formation of a particle with a cargo peptide. A partial conformational transition occurs when the complex encounters phospholipids. Deshayes et al. 2004 proposed that the membrane crossing process involves formation of a transient transmembrane pore-like structure. Conformational change of Pep-1 is not associated with complexation with its cargo but is induced upon association with the cell membrane.