FIGURE 5.

Redox property of red IscS. A, reduction of red IscS by sodium borohydride. Purified red IscS (IscS(R), 30 μm, spectrum 1) was incubated with NaBH₄ (100 μm, spectrum 2) at 4 °C for 30 min. B, reduction of wild-type IscS by sodium borohydride. Purified wild-type IscS (IscS(Y), 30 μm, spectrum 1) was incubated with NaBH₄ (100 μm, spectrum 2) at 4 °C for 30 min. C, oxidation of red IscS by H₂O₂. Purified red IscS (30 μm, spectrum 1) was incubated with H₂O₂ (10 mm, spectrum 2) at 4 °C for 10 min (spectrum 2) or 3 h (spectrum 3). D, oxidation of wild-type IscS by H₂O₂. Purified wild-type IscS (30 μm, spectrum 1) was incubated with 10 mm H₂O₂ (spectrum 2) at 4 °C for 3 h. E, relative cysteine desulfurase activity of red IscS after being treated with sodium borohydride (reduced) or H₂O₂ (oxidized). F, relative cysteine desulfurase activity of wild-type IscS after being treated with sodium borohydride or H₂O₂. The enzyme activity of purified red IscS varied in different preparations and closely correlated with the amplitudes of the absorption peak at 395 nm of pyridoxal 5′-phosphate. The total enzyme activity of red IscS shown was ∼75% of that of wild-type IscS. The results are the representatives from three independent different experiments.