(56c) Assembly Dynamics of Bacterial Pore Forming Toxins on Lipid Membranes

Single molecule fluorescence based techniques allow investigation of properties of biomolecules one at a time that can reveal underlying heterogeneity intrinsic to biological systems. This aids in unraveling mechanistic details of complex molecular assembly pathways that otherwise are inaccessible by ensemble studies. I will discuss single molecule based assays like particle tracking and photobleaching analysis that allows us to reveal complexities on lipid membrane dynamics and self-assembly of bacterial pore forming toxins.

Biomembranes, self-assembled from lipid molecules, act as a platform for the assembly of several 2D and 3D biological structures. We use bacterial pore forming toxins (PFTs) to understand biological assembly on lipid membranes. PFTs, a major class of bacterial toxins are released as water soluble monomers. Upon binding the bilayer membrane, they undergo structural rearrangements and oligomerize to form a stable transmembrane pore. The molecular mechanisms giving rise to selective pore formation on target eukaryotic membranes have been unclear. Using single molecule imaging, we dissect the assembly pathway of Cytolysin A, a representative αPFT and demonstrate how cholesterol is a key component for effective pore formation and a possible means for selective targeting of PFTs to their target cells.