Kinetics analysis of YedY activity. DMSO reductase activity of several purified fractions of YedY was measured in a glovebox with reduced benzyl viologen as electron donor and DMSO as substrate. The oxidation of benzyl viologen was spectrophotometrically monitored at 600 nm. The four enzymes were purified from R. sphaeroides strains either harboring the plasmid pSM88 for the “C-ter tag” YedY, plasmid pSM181 for the “N-ter tag (-SS)” enzyme or pSM196 for the “N-ter tag (+SS)” enzyme. The enzyme “No tag (+SS)” results from cleavage of the “N-ter tag (+SS)” enzyme with TEV protease. For each plot, at least two experiments with independent biological samples were used. Nonlinear regression of the Michaelis–Menten equation was calculated with SigmaPlot analysis software.