FIG 5.

Effects of Cys mutation on CgMsrA activity. (A) The reductase activities of CgMsrA variants were determined by monitoring the rates of NADPH oxidation as described in Materials and Methods. (B) CgMsrA-mediated protection against oxidative stress is dependent on the active-site cysteines, i.e., Cys56, Cys204, and Cys213. The ΔmsrA and ΔmsrA ΔmshC Δmrx1 mutants were transformed with pXMJ19, pXMJ19-msrA, pXMJ19-msrA:C91SC204S, pXMJ19-msrA:C91SC213S, and pXMJ19-msrA:C91SC204SC213S, respectively, and tested for sensitivity to H₂O₂ (100 mM) by survival assay. The data are means of the values obtained from three independent assays. Mean values with standard deviations (error bars) from at least three repeats are shown. *, P ≤ 0.05.