Expression and purification were done as already described by Füsser et al. with slight modifications. The vector encoding for M. smegmatis TrxR (pCDF6P) contains an N-terminal GST-His-tag for the protein and was heterogeneously overexpressed in E. coli BL21 (DE3) cells. The cells were cultivated in TB-medium with 50 µg mL -1 streptomycin at 37 °C. After reaching an OD600 of 0.6, the culture was cooled on ice for 30 minutes. The protein expression was induced by adding 1 mM IPTG and continued for 18 hours at 16 °C and 170 rpm. The cells were harvested (2,981 xg, 15 minutes, 4 °C) and stored at -20 °C until usage.