Stepwise assembly of α-hemolysin from intermediates to the mature pore in native erythrocytes.

Alpha-hemolysin (α-HL) is a small pore-forming toxin secreted by pathogenic Staphylococcus aureus, inducing cell death process by forming pores in membrane. So far, detergents or artificial lipid environments have been utilized to characterize the toxin structure. The toxin-induced changes in the membrane, membrane remodeling after toxin treatment, and the role of the toxin during pore formation process remain ambiguous. Thus, understanding pore formation in the cellular environment, including the roles of the plasma membrane and lipid composition, is crucial for drug development. In this study, we captured step-by-step oligomerization of α-HL and membrane rupture of erythrocyte cells using confocal microscopy, cryo-EM imaging, and single-particle analysis. We resolved 3.1-3.8 Å resolution structures of pore, prepore, and immature pore conformations in cellular environment. Furthermore, mass spectrometry analysis demonstrated key erythrocyte lipid components interacting with α-HL. Our findings indicate that shorter or unsaturated lipid chains facilitate pore formation and the role of phosphatidylcholine with varying physical properties in modulating the toxin's activity.