N-Formylation modifies membrane damage associated with PSMα3 interfacial fibrillation

Area of Science:

• Biochemistry
• Microbiology
• Biophysics

Background:

• Staphylococcus aureus virulence relies on phenol soluble modulins alpha3 (PSMα3) peptides.
• PSMα3 self-assemble into amyloid-like fibrils, crucial but insufficient for cytotoxicity.
• The link between PSMα3 structure, assembly, and membrane interaction remains unclear.

Purpose of the Study:

• Investigate how N-terminal charge and self-assembly influence PSMα3 interactions with model membranes.
• Elucidate the role of PSMα3 structure and assembly intermediates in membrane disruption.
• Clarify the mechanisms underlying PSMα3-induced cytotoxicity and Staphylococcus aureus pathogenesis.

Main Methods:

• In vitro studies combining atomic force microscopy (AFM) imaging and infrared spectroscopy.
• Utilized model membranes with controlled lipid compositions.
• Real-time AFM imaging to observe PSMα3 self-assembly and membrane interaction dynamics.

Main Results:

• N-terminal N-formylation of PSMα3 mediates membrane binding via electrostatic interactions with lipid head groups.
• PSMα3 insertion into lipid bilayers is favored in fluid membrane phases through hydrophobic interactions.
• Intermediate protofibrillar PSMα3 entities, not mature fibrils, promote membrane thinning and disruption.

Conclusions:

• N-formylation and intermediate self-assembling PSMα3 entities are key drivers of membrane lipid interactions and cytotoxicity.
• These findings highlight the importance of early-stage assembly intermediates in PSMα3's pathogenic mechanism.
• Understanding these interactions provides insights into Staphylococcus aureus pathogenesis and potential therapeutic targets.