Fig. 4.

NRX1 regulates redox modification and activity of catalase. (A) Protein extracts from untreated, MV- (5 µM), or Psm ES4326- (5 × 10⁵ cells) treated plants were alkylated and incubated with or without DTT (2 mM). Free thiols were labeled with biotin and pulled down with Streptavidin. Oxidized catalase (OX-CAT) was visualized by immunoblotting with an anticatalase antibody and shown relative to total catalase. (B) The ability of protein extracts from untreated, MV- (5 µM), or Psm ES4326- (5 × 10⁵ cells) treated plants to decompose H₂O₂ (5 mM) was measured at A₂₄₀ and leaf catalase activity (mmol H₂O₂⋅mg⋅protein⁻¹⋅min⁻¹) calculated using the extinction coefficient of 0.036 cm²/µmol. Error bars represent SE (n = 3). *P < 0.05 for statistical differences with WT and cat2 cat3; **P < 0.05 for statistical differences with WT and nrx1 (Student’s t test). (C) As in B, but extracts were supplemented with 4 µM recombinant NRX1 or NRX1(C55,58,375,378S) and 0.33 mM DTT. pNRX1, recombinant NRX1 protein added to reaction mixture; mut., mutant recombinant NRX1 protein. Error bars represent SE (n = 3). *P < 0.05 for statistical differences compared to mutant recombinant NRX1 protein (Student’s t test).