BIOCHEMICAL STUDIES ON THE TOXIC NATURE OF SNAKE VENOM
Final rept. no. 1, 6 May 1966-5 May 1967
KAOHSIUNG MEDICAL COLL (TAIWAN) DEPT OF BIOCHEMISTRY
Pagination or Media Count:
Clarification of the status of sulfur bonds in the biologically- active protein is very important not only for the establishment of structure but also for the elucidation of their relation to the biological activity. The total content of half cystine plus cysteine of cobrotoxin was measured to be 12. 0 by disulfide interchange reactions. No sulfhydryl groups were detected by spectrophotometric titration with p-chloromercuribenzoate and N-ethylmaleimide even after cobrotoxin was treated with 8 M urea. Since no methionine was found on amino acid analysis, the sulfurs in cobrotoxin were proved to be exclusively in the form of disulfide bonds. On reduction with -mercaptoethanol, cobrotoxin displays 11.6 to 12.0 sulfhydryl groups and loses its lethality concurrently. However, the inert, fully reduced cobrotoxin yields biologically active product with complete lethality and antigenicity, specific rotation close to the native value, and an infrared spectrum identical to native cobrotoxin on reoxidation. The results clearly indicate that the integrity of the disulfide bonds in cobrotoxin is essential for lethality. An optical rotatory dispersion ORD study was made of the native, reduced and reoxidized cobrotoxin preparations in the wavelength range 220-300 millimicrons and a positive Cotton effect at 233 millimicrons was discovered for the native cobrotoxin.