title: Subunit organisation and symmetry of pore-forming, oligomeric pneumolysin.
abstract: We present a detailed analysis of the oligomeric subunit organisation of pneumolysin by the use of negative stain electron microscopy and image processing to produce a projection density map. Analysis of the rotational symmetry has revealed a large and variable subunit number, between 40-50. The projected subunit density by rotational averaging shows at least two distinct subunit domains at different radial positions. Side views of the rings reveal further details concerning the dimensions of the oligomer in the membrane. On the basis of these observations and our previous knowledge of the monomer domain structure we propose that the 4-domain subunits are packed in a square planar arrangement to form the pneumolysin oligomer.
authors.affiliation: Department of Microbiology and Immunology, University of Leicester, UK.
authors.forename: P J
authors.initials: PJ
authors.lastname: Morgan
authors.forename: S C
authors.initials: SC
authors.lastname: Hyman
authors.forename: A J
authors.initials: AJ
authors.lastname: Rowe
authors.forename: T J
authors.initials: TJ
authors.lastname: Mitchell
authors.forename: P W
authors.initials: PW
authors.lastname: Andrew
authors.forename: H R
authors.initials: HR
authors.lastname: Saibil
mesh_terms: D001426:Bacterial Proteins; D007091:Image Processing, Computer-Assisted; D008081:Liposomes; D008854:Microscopy, Electron; D008968:Molecular Conformation; D016624:Negative Staining; D013301:Streptolysins / Q000737:chemistry*
chemical_list: D001426:Bacterial Proteins; D008081:Liposomes; D013301:Streptolysins; C032290:plY protein, Streptococcus pneumoniae