Effect of lipid composition on buforin II structure and membrane entry

Abstract

Buforin II is a 21-amino acid polycationic antimicrobial peptide derived from a peptide originally isolated from the stomach tissue of the Asian toad Bufo bufo gargarizans. It is hypothesized to target a wide range of bacteria by translocating into cells without membrane permeabilization and binding to nucleic acids. Previous research found that the structure and membrane interactions of buforin II are related to lipid composition. In this study, we used molecular dynamics (MD) simulations along with lipid vesicle experiments to gain insight into how buforin II interacts differently with phosphatidylcholine (PC), phosphatidylglycerol (PG), and phosphatidylethanolamine (PE) lipids. Fluorescent spectroscopic measurements agreed with the previous assertion that buforin II does not interact with pure PC vesicles. Nonetheless, the reduced entry of the peptide into anionic PG membranes versus neutral PC membranes during simulations correlates with the experimentally observed reduction in BF2 translocation through pure PG membranes. Simulations showing membrane entry into PC also provide insight into how buforin II may initially penetrate cell membranes. Our MD simulations also allowed us to consider how neutral PE lipids affect the peptide differently than PC. In particular, the peptide had a more helical secondary structure in simulations with PE lipids. A change in structure was also apparent in circular dichroism measurements. PE also reduced membrane entry in simulations, which correlates with decreased translocation in the presence of PE observed in previous studies. Together, these results provide molecular-level insight into how lipid composition can affect buforin II structure and function and will be useful in efforts to design peptides with desired antimicrobial and cell-penetrating properties.

Unveiling the Multifaceted Mechanisms of Antibacterial Activity of Buforin II and Frenatin 2.3S Peptides from Skin Micro-Organs of the Orinoco Lime Treefrog (Sphaenorhynchus lacteus)

“…As previously reported, BF2 is able to enter into the cytoplasmic membrane without generating significant depolarization and/or cellular leakage (Table 3). This pattern is consistent with the currently accepted mechanism of BF2 action that establishes its ability to translocate into bacteria without disrupting the membrane [9,10,11,12,13,14]. Our findings unveil for the first time the capacity of BF2 to agglutinate E. coli cells and liposomes when increasing the peptide concentration above its effective antimicrobial concentration.…”

“…BF2 inhibited the growth of both Gram-negative and Gram-positive bacteria at remarkably low micromolar concentrations (Table 2). As reported previously for BF2 peptides purified from other species [9,10,11,12,13,14], our results highlight the BF2 elevated bactericidal activity. In regard to F2.3S and as predicted by in silico analysis, this peptide also presented a potent antibacterial activity against both E. coli and S. aureus reference cultures (Table 2).…”

“…Interestingly, BF2 membrane translocation is independent of any cellular receptor and the peptide can readily enter both bacterial cells and liposomes [9,10]. Previous studies have shown the important role of proline in the ability of the peptide to translocate across the bacterial membrane by the formation of transient toroidal pores [11,12,13,14]. Furthermore, some studies have shown that buforin can act synergistically with other antibiotics such as cefazolin, thereby increasing the antibacterial action and its activity against biofilms [12,15].…”

Novel histone-derived antimicrobial peptides use different antimicrobial mechanisms

“…In particular, a proline hinge may be more likely to induce translocation in peptides with less amphipathic character that do not readily form stable membrane-disrupting structures, such as DesHDAP1 and BF2, by increasing their ability to interact with lipids upon membrane entry. In fact, deformations around proline that increase membrane interactions have been observed in molecular dynamics simulations of BF2 interacting with lipid membranes [30]. The inclusion of a proline hinge may be less effective in inducing translocation in peptides that exhibit greater lytic potential, such as DesHDAP3, although additional examples of similar peptides with these properties would be helpful to support this assertion.…”

Modular analysis of hipposin, a histone-derived antimicrobial peptide consisting of membrane translocating and membrane permeabilizing fragments

“…Table 1 notes how these sequences compare to the physiological sequences of hipposin, buforin I (BF1), buforin II (BF2) and parasin. Notably, the HipB region that was analogous to buforin II (BF2) included the F10W mutation that has been widely used in previous studies and shown to have analogous properties to the wildtype peptide [15, 16, 18, 20, 21]. …”