title: Conformational alteration in alpha-toxin from Staphylococcus aureus concomitant with the transformation of the water-soluble monomer to the membrane oligomer.
abstract: The membrane-damaging alpha-toxin aggregate of Staphylococcus aureus was characterized physicochemically. The aggregate weight of the toxin formed by various methods appeared to be 6 times higher than the molecular weight of the monomer as determined by the laser light scattering technique, suggesting the presence of a hexamer in the membrane. The aggregates fluoresced 20 to 50% more than the monomer at 336 nm. Circular dichroism measurements revealed that both the monomer and the oligomer showed essentially beta-sheet structure with the maximum ellipticity about -8,400 deg.cm2.dmol-1 at 215 nm. Circular dichroism spectrum of the oligomers showed ellipticity difference of -6,600, -44 and +84 deg.cm2.dmol-1, at 200, 250 and 280 nm, respectively, compared with the monomer. All these results suggest that the conformational change in the toxin molecule occurs concomitant with the transformation of the water-soluble monomer to the membrane-embedded hexamer.
mesh_terms: D001427:Bacterial Toxins; D002942:Circular Dichroism; D006460:Hemolysin Proteins; D046911:Macromolecular Substances; D008565:Membrane Proteins; D008566:Membranes; D008970:Molecular Weight; D011487:Protein Conformation; D012995:Solubility; D013050:Spectrometry, Fluorescence; D013211:Staphylococcus aureus
chemical_list: D001427:Bacterial Toxins; D006460:Hemolysin Proteins; D046911:Macromolecular Substances; D008565:Membrane Proteins; C021091:staphylococcal alpha-toxin