title: Disulfide-bond scanning reveals assembly state and β-strand tilt angle of the PFO β-barrel.
abstract: Perfringolysin O (PFO), a bacterial cholesterol-dependent cytolysin, binds a mammalian cell membrane, oligomerizes into a circular prepore complex (PPC) and forms a 250-Å transmembrane β-barrel pore in the cell membrane. Each PFO monomer has two sets of three short α-helices that unfold and ultimately refold into two transmembrane β-hairpin (TMH) components of the membrane-embedded β-barrel. Interstrand disulfide-bond scanning revealed that β-strands in a fully assembled PFO β-barrel were strictly aligned and tilted at 20° to the membrane perpendicular. In contrast, in a low temperature-trapped PPC intermediate, the TMHs were unfolded and had sufficient freedom of motion to interact transiently with each other, yet the TMHs were not aligned or stably hydrogen bonded. The PFO PPC-to-pore transition therefore converts TMHs in a dynamic folding intermediate far above the membrane into TMHs that are hydrogen bonded to those of adjacent subunits in the bilayer-embedded β-barrel.
authors.affiliation: Department of Molecular and Cellular Medicine, Texas A&M Health Science Center, College Station, Texas, USA.
authors.forename: Takehiro K
authors.initials: TK
authors.lastname: Sato
authors.forename: Rodney K
authors.initials: RK
authors.lastname: Tweten
authors.forename: Arthur E
authors.initials: AE
authors.lastname: Johnson
mesh_terms: D001427:Bacterial Toxins / Q000737:chemistry*; D002462:Cell Membrane / Q000378:metabolism; D002784:Cholesterol / Q000737:chemistry; D003016:Clostridium perfringens / Q000378:metabolism; D003432:Cross-Linking Reagents / Q000737:chemistry; D019281:Dimerization; D004220:Disulfides; D004926:Escherichia coli / Q000378:metabolism; D006460:Hemolysin Proteins / Q000737:chemistry*; D008081:Liposomes / Q000737:chemistry; D008968:Molecular Conformation; D009154:Mutation; D011485:Protein Binding; D017433:Protein Structure, Secondary; D013696:Temperature; D014357:Trypsin / Q000737:chemistry
chemical_list: D001427:Bacterial Toxins; D003432:Cross-Linking Reagents; D004220:Disulfides; D006460:Hemolysin Proteins; D008081:Liposomes; C020452:Clostridium perfringens theta-toxin; D002784:Cholesterol; D014357:Trypsin
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