Assemblies of pore-forming toxins visualized by atomic force microscopy

• PFTs oligomerize into well-defined structures on lipid bilayers.
• Oligomeric structures of PFTs can be resolved by AFM.
• Binding of PFTs to lipid bilayers may induce membrane reorganization.
• Dynamics of PFT oligomers can be monitored by high-speed AFM.

A number of pore-forming toxins (PFTs) can assemble on lipid membranes through their specific interactions with lipids. The oligomeric assemblies of some PFTs have been successfully revealed either by electron microscopy (EM) and/or atomic force microscopy (AFM). Unlike EM, AFM imaging can be performed under physiological conditions, enabling the real-time visualization of PFT assembly and the transition from the prepore state, in which the toxin does not span the membrane, to the pore state. In addition to characterizing PFT oligomers, AFM has also been used to examine toxin-induced alterations in membrane organization. In this review, we summarize the contributions of AFM to the understanding of both PFT assembly and PFT-induced membrane reorganization. This article is part of a Special Issue entitled: Pore-Forming Toxins edited by Mauro Dalla Serra and Franco Gambale.

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