Insights into Membrane Translocation of Protegrin Antimicrobial Peptides by Multistep Molecular Dynamics Simulations

Abstract

Protegrin-1 (PG-1) is a cationic arginine-rich antimicrobial peptide. It is widely accepted that PG-1 induces membrane disruption by forming pores that lead to cell death. However, the insertion mechanism for these highly cationic peptides into the hydrophobic membrane environment is still poorly understood at the molecular scale. It has previously been determined that the association of arginine guanidinium and lipid phosphate groups results in strong bidentate bonds that stabilize peptide–lipid complexes. It has also been suggested that arginine residues are able to drag phosphate groups as they insert inside the membrane to form a toroidal pore. However, whether bidentate bonds play a significant role in inducing a pore formation remains unclear. To investigate the role of bidentate complexes in PG-1 translocation, we conducted molecular dynamics simulations. Two computational electroporation methods were implemented to examine the translocation process. We found that PG-1 could insert into the membrane, provided the external electric potential is large enough to first induce a water column or a pore within the lipid bilayer membrane. We also found that the highly charged PG-1 is capable in itself of inducing molecular electroporation. Substitution of arginines with charge-equivalent lysines showed a markedly reduced tendency for insertion. This indicates that the guanidinium group likely facilitates PG-1 translocation. Potential of mean force calculations suggests that peptide insertion inside the hydrophobic environment of the membrane core is not favored. We found that formation of a water column or a pore might be a prerequisite for PG-1 translocation. We also found that PG-1 can stabilize the pore after insertion. We suggest that PG-1 could be a pore inducer and stabilizer. This work sheds some light on PG-1 translocation mechanisms at the molecular level. Methods presented in this study may be extended to other arginine-rich antimicrobial and cell-penetrating peptides.

Bioactivity and Bactericidal Mechanism of Histidine-Rich β-Hairpin Peptide Against Gram-Negative Bacteria

“…When n = 2, symmetrical-end polypeptides show higher antimicrobial efficacy compared with that of PG-1 [7]. Furthermore, since arginine residues are electrostatically attracted to the bacterial cell membrane and can bind the peptides to the phospholipid membrane to enhance their antibacterial activity [15,16], two arginine residues are added to the symmetric ends of the peptides. Finally, the amidation of the C-terminus increases the positive charge of the peptides and increases their structural stability, thus facilitating their translocation into the bacterial inner membrane.…”

Identification and elucidation of proline‐rich antimicrobial peptides with enhanced potency and delivery

“…From this study, Bac7(1–16) seems to lose SbmA dependency in diluted MHB medium. Because of the high arginine content, 8 out of 16 residues, Bac7(1–16) might possess similar transportation mechanisms as the arginine‐rich cell‐penetrating peptides via the formation of bidentate bonds (Lai & Kaznessis ; Pantos, Tsogas, & Paleos ; Su, Li, & Hong ; Tang, Waring, & Hong ) or perhaps gain cell entry via a different mechanism.…”

Protegrin-1 cytotoxicity towards mammalian cells positively correlates with the magnitude of conformational changes of the unfolded form upon cell interaction

“…This view was also justified by a study in which cationic β-hairpin AMP SVS-1 was fully folded and was active only in the presence of a charged membrane 38 . In addition, arginine in PG-1 interacts with the phosphate atoms of lipid membranes through series of bidentate network of bonds and helps the translocation of PG-1 48 .…”