Synthetic copoly(Lys/Phe) and poly(Lys) translocate through lipid bilayer membranes

Abstract

Several membrane-transporting peptides (MTP) containing basic amino acid residues such as Lys and Arg that carry macromolecules such as DNA and proteins across cell plasma membranes by an unknown mechanism have been actively studied. On the basis of these results, we have been investigating the translocation ability of synthetic polypeptides, copoly(Lys/Phe) and poly(Lys), through negatively charged phospholipid (soybean phospholipid (SBPL)) bilayer membranes by zeta potential analysis, circular dichroism (CD) spectroscopy, fluorescence spectroscopy, an electrophysiology technique, and confocal laser scanning microscopy (CLSM). The binding of these polypeptides to the membrane, which is the first step for translocation across the membrane, resulted in the conformational transition of the polypeptide from a random coil form or helix-poor form to a helix-rich form. The fluorescence studies demonstrated that the time-dependent decrease in the fluorescence intensities of the FITC-labeled polypeptides bound to the SBPL liposome reflected translocation of the polypeptide across the lipid bilayer with the low dielectric constant. Both the rate constant and the efficiency of the polypeptide translocation across the lipid bilayer were greater for copoly(Lys/Phe) than for poly(Lys). These results suggest that the random incorporation of the hydrophobic Phe residue into the positively charged Lys chain results in a lowering of the potential barrier for passage of the polypeptide in the hydrophobic core portion of the lipid bilayer. We presented the first direct observation that the positively charged polypeptides, copoly(Lys/Phe) (MW: 41,500) and poly(Lys) (MW: 23,400), could translocate across the lipid bilayer membrane.

Poly-l-lysines and poly-l-arginines induce leakage of negatively charged phospholipid vesicles and translocate through the lipid bilayer upon electrostatic binding to the membrane

“…fluid or gel phase, and for both a short and a long polymer. Table 1 Similar findings were reported earlier by Shibata et al [20] who probed the translocation ability of FITC-PLL 106 (from the same supplier) through soybean phospholipid membranes with confocal microscopy.…”

“…This effect plays a role in the cellular uptake of viruses [11,12] and oligonucleotides [6]. Also, PLL and PLA are able to translocate through lipid membranes without being complexed as shown by Shibata et al [20] and Sakai & Matile [4].…”

Peptide-Based Polymer Therapeutics

“…Significant differences among treated and non-treated animals were observed, validating them as a possible therapy in glomerular diseases [145]. Poly(phenylalanine) has been also used for this purpose, either as part of an amphiphilic multi-armed copolymer using poly(ethyleneimine) (PEI) as macroinitiator achieving gene transfection in vitro [146] or co-polymerised with other molecules such as PLL (poly(lysine-co-phenylananine) observing translocation across the lipid bilayer and subsequent drug release into the cytoplasm [147].…”

Effect of Tryptophan Residues on Adsorption of a Cationic Arginine Rich Polypeptide by Hydroxyapatite Nanoparticles and Following Translocation of the Polypeptide Through a Lipid Vesicle Membrane

“…We have reported elsewhere [23][24][25][26] that cationic polymers, such as L-lysine, L-tyrosine copolymer, poly-L-lysine, poly-L-arginine, and polyethyrenimine, could translocate across a lipid bilayer membrane [23][24][25] and that the transporting ability of poly-L-arginine is dominated by its secondary structure 26 .…”