title: Real-time visualization of assembling of a sphingomyelin-specific toxin on planar lipid membranes.
abstract: Pore-forming toxins (PFTs) are soluble proteins that can oligomerize on the cell membrane and induce cell death by membrane insertion. PFT oligomers sometimes form hexagonal close-packed (hcp) structures on the membrane. Here, we show the assembling of the sphingomyelin (SM)-binding PFT, lysenin, into an hcp structure after oligomerization on SM/cholesterol membrane. This process was monitored by high-speed atomic force microscopy. Hcp assembly was driven by reorganization of lysenin oligomers such as association/dissociation and rapid diffusion along the membrane. Besides rapid association/dissociation of oligomers, the height change for some oligomers, possibly resulting from conformational changes in lysenin, could also be visualized. After the entire membrane surface was covered with a well-ordered oligomer lattice, the lysenin molecules were firmly bound on the membrane and the oligomers neither dissociated nor diffused. Our results reveal the dynamic nature of the oligomers of a lipid-binding toxin during the formation of an hcp structure. Visualization of this dynamic process is essential for the elucidation of the assembling mechanism of some PFTs that can form ordered structures on the membrane.
authors.affiliation: Lipid Biology Laboratory, RIKEN, Wako, Saitama, Japan.
authors.forename: Neval
authors.initials: N
authors.lastname: Yilmaz
authors.forename: Taro
authors.initials: T
authors.lastname: Yamada
authors.forename: Peter
authors.initials: P
authors.lastname: Greimel
authors.forename: Takayuki
authors.initials: T
authors.lastname: Uchihashi
authors.forename: Toshio
authors.initials: T
authors.lastname: Ando
authors.forename: Toshihide
authors.initials: T
authors.lastname: Kobayashi
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000737:chemistry* / Q000378:metabolism; D002784:Cholesterol / Q000378:metabolism; D004058:Diffusion; D008051:Lipid Bilayers / Q000737:chemistry* / Q000378:metabolism; D018625:Microscopy, Atomic Force; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D013109:Sphingomyelins / Q000378:metabolism*; D013499:Surface Properties; D013997:Time Factors; D014118:Toxins, Biological / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D008051:Lipid Bilayers; D013109:Sphingomyelins; D014118:Toxins, Biological; C107040:lysenin; D002784:Cholesterol
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