FIGURE 5.
MSR reduces the heme- but not hemoglobin-bound polysulfides. A, FeIII-Hb (100 μm heme) was mixed with 0.5 mm Na2S in 100 mm HEPES buffer, pH 7.4, and incubated aerobically for 30 min at 25 °C before the addition of MSR and NADPH, after which incubation was continued for 3 h. Then the sulfane sulfur levels were measured in the protein-bound and -free fractions as described under “Experimental Procedures.” The data represent the mean ± S.D. (error bars) of three independent experiments. B, spectrum of FeIII-Hb after treatment with Na2S for 30 min (red) followed by a 1-h incubation with MSR and NADPH (black). Conditions are the same as in A except that the samples were diluted 1:10 with 100 mm HEPES, pH 7.4.