RT-A(cs2) corresponds to a mutated version of the catalytic A chain encoded by the Ricinus communis ricin toxin (RT) gene (UniProtKB:P02879); it carries a single amino acid substitution (G212R) in the active site cleft (FBrf0055886). The wild-type RT A chain can be used as a cell ablation tool; it inhibits eukaryotic protein synthesis via hydrolysis of a specific N-glycosidic bond in 28S rRNA, inactivating the ribosome (PMID:3288622). The G212R mutation in RT-A(cs2) renders the protein cold-sensitive; extensive cell death is seen at 29[o]C when RT-A(cs2) is expressed in transgenic flies, but at 18[o]C almost no cell death is seen. In addition, the activity of RT-A(cs2) appears to be attenuated compared to wild-type RT-A (FBrf0152363). Since the RT-A(cs2) sequence does not include the B chain or the secretory signal peptide normally also encoded by the Ricinus communis RT gene (PMID:2999712), the cell ablation caused by RT-A(cs2) is expected to be cell autonomous (FBrf0055886).