A Molecular View on the Interaction of the Trojan Peptide Penetratin with the Polar Interface of Lipid Bilayers

Abstract

Penetratin belongs to the family of Trojan peptides that effectively enter cells and therefore can be used as cargoes for agents that are unable to penetrate the cell membrane. We applied polarized infrared spectroscopy in combination with the attenuated total reflection technique to extract information before penetratin binding to lipid membranes with molecular resolution. The amide I band of penetratin in the presence of zwitterionic dimyristoylphosphatidylcholine and of anionic lipid membranes composed of dioleoylphosphatidylcholine and dioleoylphosphatidylglycerol shows the characteristics of an antiparallel beta-sheet with a small fraction of turns. Both signatures have been interpreted in terms of a hairpin conformation. The infrared linear dichroism of the amide I band indicates that the peptide chain orients in an oblique fashion whereas the plane of the sheet aligns virtually parallel with respect to the membrane surface. The weak effect of the peptide on dimyristoylphosphatidylcholine gives indication of its superficial binding where the charged lysine and arginine side chains form H-bonds to the phosphate oxygens of the surrounding lipids. The determinants for internalization of penetratin appear to be a peptide sequence with a distribution of positively charged residues along a beta-sheet conformation, which enables the anchoring of the peptide in the polar part of the membranes and the effective compensation of anionic lipid charges.

Structure and dynamics of Penetratin’s association and translocation to a lipid bilayer

“…The structures observed in these simulations are in good agreement with previous computational findings, 13 and with NMR experiments; 7 there is a small difference in terms of the both termini, where some studies find turns instead of coils. Unlike other experimental results 8,24 no β−sheet conformations were found here.…”

Cell-penetrating peptides as a promising tool for delivery of various molecules into the cells

“…This was confirmed by the results obtained from experiments using nuclear magnetic resonance (NMR) [29]. This mechanism is driven mainly by the CPP gradients on both sides of the cell membrane [30].…”

Arginine-rich cell penetrating peptides: from endosomal uptake to nuclear delivery

“…On the other hand, penetratin changes its conformation upon binding to lipid bilayers containing anionic lipid phosphatidylglycerol (PG), from a mostly random-coiled structure in the buffer to more a-helixal and b-sheet conformations on the lipid bilayers [70][71][72][73]. However, penetratin does not insert into the lipid bilayer, remaining on the surface [72,74]. Addition of cholesterol inhibits the binding of penetratin to liposomes composed of zwitterionic phosphatidylcholine (PC) and anionic phosphatidylserine [75].…”

“…While no translocation of TAT through the lipid bilayer has been observed [78], several groups have demonstrated translocation of penetratin through the protein-free lipid bilayer, and several mechanisms of such translocation have been proposed. An electroporation-like mechanism of penetratin translocation through charged lipid bilayers has been proposed by Binder et al [74,79]. These authors suggest that binding of penetratin to the outer monolayer neutralizes the surface charge of anionic lipids and leads to the development of a transmembrane electrical fi eld that is known to result in the formation of transient pores in protein-free lipid bilayers [80][81][82].…”