Hydrophobic interaction chromatography of Staphylococcus aureus delta-toxin

Staphylococcus aureus delta-toxin bound avidly to agarose gels containing phenyl, octyl, or decyl ligands, but less so to agarose with hexyl groups. Agarose with ethyl or butyl moieties did not bind any more toxin than did agarose without attached ligands. About 10% of the applied toxin preparation did not bind to gels and eluted with the starting buffer. The nonadsorbed material was not hemolytic, did not react with anti-delta-toxin immunoglobulin G, and did not appear to be a peptide. Toxin bound to phenyl-Sepharose was not eluted with water, solutions containing chaotropic ions or ethylene glycol, or by increasing the pH, but was eluted with 50% ethanol. The ethanol-eluted delta-toxin (EEDT) was soluble in water, ethanol, 10% sucrose, or 6 M urea, but was poorly soluble in aqueous salt solutions at neutral pH. Regardless of whether the soluble or insoluble form of delta-toxin was applied to the gel, the resultant EEDT fraction was water soluble. The hemolytic activity of EEDT was markedly reduced when assayed in saline, but was the same as that of the original toxin preparation when assayed in isotonic sucrose. A significant portion of EEDT, when rechromatographed on phenyl-Sepharose, did not bind to the gel. This unbound fraction may represent toxin aggregates in which the hydrophobic regions of the toxin monomers are interiorized within the aggregates.