Figure 6. Disposal of RTB involved interaction with the CNX cycle in a manner that did not interfere with incoming ricin.

(A) Quantification of RTB in cell extracts after electrophoresis using a PhosphorImager. Results are displayed graphically, plotting the proportion of RTB retained in cell extracts against the time of chase, for cells treated with CST (○) or DMM (□), compared with untreated cells from Figure 5 (- - - -). (B) Effect of CST and DMM on cytotoxicity of ricin. HeLa cells (grey triangles) and HeLa/RTB-H2 cells (grey circles) were challenged for 4 h with increasing concentrations of ricin and their ability to incorporate [³⁵S]methionine into proteins was determined and expressed as the proportion of remaining protein synthesis. In parallel, cells were treated with CST (▵, HeLa; ○, HeLa/RTB-H2) or DMM (grey squares, HeLa; □, HeLa/RB-H2) during the intoxication process.