TXNL6-mediated MsrA repair of cytochrome c inhibits cytochrome c peroxidase activity.

<p>Representative graph (from 3 independent experiments) of cytochrome c (cyt c) mediated peroxidase activity. The graph shows mean values for an N of 3 ± SD. Cyt c oxidized (cyt c ox) (incubated for 15 min with a 4∶1 molar ratio of HOCl) is 100% peroxidase activity, all other activities are expressed as a percentage of the cyt c ox activity. The untreated cyt c protein has 16% cyt c peroxidase activity compared to cyt c ox. Cyt c ox incubated with MsrA in the absence of a reducing system has 91% activity of the oxidized. Treatment of the cyt c ox (291 µM) with MsrA (1.9 µM for 2 h at 37°C) and TXNL6 (1.39 µM) with thioredoxin reductase (TxrR) and NADPH leads to a statistically significant (p<0.001) 48% decrease in peroxidase activity. Similarly treatment of cyt c ox with MsrA and either Trx 1 or Trx 2 (both 1.39 µM) with TxrR/NADPH also significantly (p<0.001) decreased both peroxidase activities by 52% and 54% respectively. Incubation of cyt c ox with MsrA and TXNL6 in the absence of TxrR/NADPH resulted in just a 14% decrease in cyt c peroxidase activity while incubation of cyt c ox with TXNL6 and TxrR/NADPH in the absence of MsrA resulted in 19% decrease in cyt c peroxidase activity. p values were obtained using Tukey's test following one-way ANOVA.