Biochemical Studies on Streptolysin S'

III. Polypeptide-Oligoribonucleotide Complex Nature of the Toxin

抄録

The chemical nature of streptolysin S' was studied with the purified C¹⁴-labeled toxin and the following findings were obtained.
1. The purified C¹⁴-labeled toxin was inactivated and digested by Nagarse, but neither inactivated nor digested by trypsin. This fact indicated that amino acids existed in the toxin molecule as polypeptide (or protein) susceptible to Nagarse but not to trypsin.
2. The RNase T₁ digestion of the oligo-ribonucloetide portion changed the behavior of the polypeptide against a Sephadex G-75 column.
3. The pH 10.5 treatment gave a con-siderably different gel-filtration pattern from that of the native toxin.
4. The phenol treatment of the toxin removed the polypeptide moiety from most part of the oligoribonucleotides.
5. The transfer of the hemolytic activity to Tween 40 fractions was observed by the incubation of the toxin with the detergent, as Ginsburg et al. reported. Furthermore the formation of a polypeptide-Tween complex with hemolytic activity was demonstrated.
6. The toxin was precipitated by salmine sulfate and inactivated by 8M urea but neither by 6M guanidine hydrocholoride nor by 8M NaCl.
From these results, it was concluded that streptolysin S' was a polypeptide (or protein)-oligoribonucleotide complex and the former was an essential toxic component.
The present authors wish to express their sincere thanks to Mr. Y. Sokawa for his useful discussions.