title: Self-interaction of pneumolysin, the pore-forming protein toxin of Streptococcus pneumoniae.
abstract: The pathogenically important cholesterol-binding pore-forming bacterial "thiol-activated" toxins (TATs) are commonly believed to be monomeric in solution and to undergo a transition on membrane binding mediated by cholesterol to an oligomeric pore. We present evidence, gained through the application of a number of biochemical and biophysical techniques with associated modelling, that the TAT from Streptococcus pneumoniae, pneumolysin, is in fact able to self-associate in solution to form the same oligomeric structures. The weak interaction leading to solution oligomerization is manifested at low concentrations in a dimeric toxin form. The inhibition of toxin self-interaction by derivatization of the single cysteine residue in pneumolysin with the thiol-active agent dithio (bis)nitrobenzoic acid indicates that self-interaction is mediated by the fourth domain of the protein, which has a fold similar to other proteins known to self-associate. This interaction is thought to have implications for the understanding of mechanisms of pore formation and complement activation by pneumolysin.
authors.affiliation: Department of Biochemistry, University of Leicester, Leicester, LE1 7RH, UK. gilbert@bioch.ox.ac.uk
authors.forename: R J
authors.initials: RJ
authors.lastname: Gilbert
authors.forename: J
authors.initials: J
authors.lastname: Rossjohn
authors.forename: M W
authors.initials: MW
authors.lastname: Parker
authors.forename: R K
authors.initials: RK
authors.lastname: Tweten
authors.forename: P J
authors.initials: PJ
authors.lastname: Morgan
authors.forename: T J
authors.initials: TJ
authors.lastname: Mitchell
authors.forename: N
authors.initials: N
authors.lastname: Errington
authors.forename: A J
authors.initials: AJ
authors.lastname: Rowe
authors.forename: P W
authors.initials: PW
authors.lastname: Andrew
authors.forename: O
authors.initials: O
authors.lastname: Byron
mesh_terms: D001426:Bacterial Proteins; D002499:Centrifugation, Density Gradient; D046911:Macromolecular Substances; D008854:Microscopy, Electron; D008958:Models, Molecular; D009502:Neutrons; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry; D012542:Scattering, Radiation; D013053:Spectrophotometry; D013296:Streptococcus pneumoniae / Q000737:chemistry*; D013301:Streptolysins / Q000737:chemistry*
chemical_list: D001426:Bacterial Proteins; D046911:Macromolecular Substances; D011994:Recombinant Proteins; D013301:Streptolysins; C032290:plY protein, Streptococcus pneumoniae