... RTB and the cytotoxicity of each of the resultantricin variants was compared to wild-type ricin. RicinR213A and ricin R213D were 12-fold and more than 2000-fold less cytotoxic than ricin, ... ricin R213A, j;andricinR213D, m.(B)ricin,d; ricin R258A, j, and ricin R258D, m;(C)ricin,d; ricin R48A, j.Fig. 2. Assessment of the N-glycosidase activity of RTA variants con-taining arginine ... between them.Cytotoxicity of RTA N78SRTA N78S was reassociated with RTB and its cytotoxicitywas compared to ricin (Fig. 5B). Ricin containing RTAN78S was approximately twofold less cytotoxic than...