Self-interaction of pneumolysin, the pore-forming protein toxin of Streptococcus pneumoniae

• Published in: Journal of molecular biology Vol. 284; no. 4; pp. 1223 - 1237
• Main Authors: Gilbert, Robert J.C., Rossjohn, Jamie, Parker, Michael W., Tweten, Rodney K., Morgan, Peter J., Mitchell, Timothy J., Errington, Neil, Rowe, Arthur J., Andrew, Peter W., Byron, Olwyn
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 11.12.1998
• Subjects: analytical ultracentrifugation; Bacterial Proteins; Centrifugation, Density Gradient; electron microscopy; Macromolecular Substances; Microscopy, Electron; Models, Molecular; neutron scattering; Neutrons; oligomerization; pneumolysin; Protein Conformation; Recombinant Proteins - chemistry; Scattering, Radiation; Spectrophotometry; Streptococcus pneumoniae; Streptococcus pneumoniae - chemistry; Streptolysins - chemistry; neutron scattering; analytical ultracentrifugation; oligomerization; DTNB; SANS; TAT; EM; electron microscopy; TNB; pneumolysin; Ply; AUC
• ISSN: 0022-2836; 1089-8638
• DOI: 10.1006/jmbi.1998.2258

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.