Rhodanese (TST) sequence comparison and purity of recombinant human TSTD1. A, sequence alignment of active-site sequences in the human sulfurtransferases: TST, MST, B. phytofirmans PRF (BpPRF); and TSTD1, TSTD2, and TSTD3. The conserved active-site cysteine is highlighted in yellow. B, recombinant human TSTD1 (20 μg) was estimated to be >95% pure by SDS-PAGE analysis and Coomassie Blue staining. Molecular mass markers (in kDa) are shown on the left.