Membrane binding of pore-forming γ-hemolysin components studied at different lipid compositions

Abstract

Methicillin-resistant Staphylococcus aureus is is among those pathogens currently posing the highest threat to public health. Its host immune evasion strategy is mediated by pore-forming toxins (PFTs), among which the bi-component γ-hemolysin is one of the most common. The complexity of the porogenesis mechanism by γ-hemolysin poses difficulties in the development of antivirulence therapies targeting PFTs from S. aureus, and sparse and apparently contrasting experimental data have been produced. Here, through a large set of molecular dynamics simulations at different levels of resolution, we investigate the first step of pore formation, and in particular the effect of membrane composition on the ability of γ-hemolysin components, LukF and Hlg2, to steadily adhere to the lipid bilayer in the absence of proteinaceous receptors. Our simulations are in agreement with experimental data of γ-hemolysin pore formation on model membranes, which are here explained on the basis of the bilayer properties. Our computational investigation suggests a possible rationale to explain experimental data on phospholipid binding to the LukF component, and to hypothesise a mechanism by which, on purely lipidic bilayers, the stable anchoring of LukF to the cell surface facilitates Hlg2 binding, through the exposure of its N-terminal region. We expect that further insights on the mechanism of transition between soluble and membrane bound-forms and on the role played by the lipid molecules will contribute to the design of antivirulence agents with enhanced efficacy against methicillin-resistant S. aureus infections.

Cryo-EM-based structural insights into supramolecular assemblies of γ-Hemolysin from Staphylococcus aureus reveal the pore formation mechanism

“…This could only be possible if the individual monomeric states bind to lipid surface partially horizontal to its crystallographic axis. Such relative orientational preference of monomeric components was further supported by a recent molecular dynamics study 51 . In addition, the superimposition of monomers upon protomers further elucidated that the critical positioning of N-terminal segments from adjacent protomeric HlgA might influence in destabilizing the surfaces of top segments of cap and pre-stem by a strong steric interference on the nearby hydrophobic and polar residues present in the top part of both monomeric subunits (HlgA and HlgB) respectively (Figure 6B, S23, S24).…”