Modelling of Fibrillation Induced Selective Cytotoxicity of Phenol Soluble Modulin α3

Phenol soluble modulin (PSM) α3, the most toxic member of α-toxin in Staphylococcus aureus bacteria, has been recently found to form cross-α amyloid fibrils and is selectively toxic to the mammalian cell membranes. In this work, it has been discovered that hydrophobic interactions play a major role in fibril formation of PSM-α3 strands, with
stabilization energy of 28.7 kCal/mol. We considered two model bilayers mimicking mammalian and bacterial cell membranes, and found that single α-helix strand penetration is energetically unfavourable in both of them. Hence, we propose a simple model using energetics to understand the reason for selective toxicity of the peptide to the mammalian cell membrane. This study, besides enhancing the understanding of PSM-α3, can also act as a stepping stone in future drug development against ​S. aureus.