DT-A(I) corresponds to a mutated version of the catalytic A subunit encoded by the Corynephage beta Diphtheria toxin (DT) gene (UniProtKB:P00588), in which a translational stop has been introduced at codon 37. DT-A(I) can be used as a cell ablation tool (it is likely that rather than DT-A(I) acting as a truncated protein, rare readthrough occurs at residue 37) (FBrf0055894). DT-A(I) was originally selected as a temperature-sensitive tool, with FBrf0055894 reporting stronger effects at 18[o]C than at 28[o]C in transgenic Drosophila. However, a subsequent paper (FBrf0123036) could not obtain adult flies at any temperature when DT-A(I) was expressed in the ovary.