FIGURE 3.

Nitrate reductase activity and total MPT content of different E. coli sulfurtransferase mutant strains. Nitrate reductase activity was determined by using cell lysates of the mutant strains CL100 (ΔiscS), JLD42301 (ΔynjE), and PJ18 (ΔiscS/ΔynjE), which were grown anaerobically in the presence of 20 mm nitrate (white bars). Reduced benzyl viologen was used as electron donor. The activity of the wild type strain was set to 100%. Shown is total MPT content of the strains CL100 (ΔiscS), JLD42301 (ΔynjE), and PJ18 (ΔiscS/ΔynjE). MPT was quantified after conversion to its fluorescence derivative Form A and is shown as relative fluorescence quantified from the peak areas (black bars). The fluorescence obtained from the wild type strain was set to 100%. Fluorescence was monitored with excitation at 383 nm and emission at 450 nm. Nitrate reductase activities and fluorescence were normalized to the optical density of cell suspensions determined at 600 nm. Error bars, S.E.