title: The heptameric prepore of a staphylococcal alpha-hemolysin mutant in lipid bilayers imaged by atomic force microscopy.
abstract: We have used atomic force microscopy to study the oligomeric state of a genetically engineered mutant of staphylococcal alpha-hemolysin (alphaHL-H5) that can be arrested as a "prepore" assembly intermediate. AFM images of alphaHL-H5 on supported bilayers of a fluid-phase lipid, egg-yolk phosphatidylcholine (egg-PC), under conditions that lock alphaHL-H5 into the prepore state, clearly show a heptameric structure for many individual oligomers. The central dent of the prepore has a diameter of 3.2 +/- 0.2 nm. The distance between the centers of mass of neighboring subunits is 2.8 +/- 0.3 nm. The heptamer has an average diameter of 8.9 +/- 0.6 nm. These results support a recently proposed pathway for the assembly of alpha-hemolysin.
authors.affiliation: Department of Physics, University of Vermont, Cook Building, Burlington, Vermont 05405, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Fang
authors.forename: S
authors.initials: S
authors.lastname: Cheley
authors.forename: H
authors.initials: H
authors.lastname: Bayley
authors.forename: J
authors.initials: J
authors.lastname: Yang
mesh_terms: D001427:Bacterial Toxins / Q000737:chemistry* / Q000235:genetics; D006460:Hemolysin Proteins / Q000737:chemistry* / Q000235:genetics; D008051:Lipid Bilayers; D018625:Microscopy, Atomic Force; D009154:Mutation; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics
chemical_list: D001427:Bacterial Toxins; D006460:Hemolysin Proteins; D008051:Lipid Bilayers; D011994:Recombinant Proteins; C021091:staphylococcal alpha-toxin