Effects of Physical and Chemical Treatments on the Biological Activity of Ricin D

Abstract

Effects of physical and chemical treatments on the cytoagglutinating activity, toxicity and inhibitory activity of cell-free protein synthesis of ricin D or its constituent polypeptide chains were investigated. The results indicated. that the isolated polypeptide chains were much less stable than intact ricin D in acidic pH, heating as well as chemicals, and the Ala chain was more unstable than the lie chain. Chemical modifications of ricin D with specific reagents revealed that the tryptophan and tyrosine residues as well as the carboxyl groups participated in the phenomena of cytoagglutination and toxic action of ricin D, whereas arginine residues were considered not to be directly involved. Trinitrophenylation of free amino groups did not result in a loss of cytoagglutinating activity, whereas caused a loss of toxicity, suggesting that free amino groups in the lie chain were involved in the toxic action of ricin D.