(A–C) Reduction levels of
Prx-QAt under the redox conditions were determined by AMS
labeling. The purified Prx-QAt was in the oxidized form. A
total of 3 μM of Prx-QAt was incubated with 50 μM
CuCl2 or the indicated concentration of DTT in the absence
(A) or presence of 4 μM (B) or 0.04
μM (C) Trx-m. Then the reduction level
of Prx-QAt was determined by the incorporation of AMS and
the change of the mobility during SDS/PAGE. (D)
Trx-m dependent peroxidase activity of
Prx-QAt was measured with H2O2 as a
substrate and NADPH as a reductant. The decrease in the absorbance at
340 nm was monitored (trace e). In traces
a–c, Trx-m, Trx
reductase, or Prx-QAt was omitted from the reaction
mixture, respectively. In trace d,
Trx-mC41S was used instead of
Trx-m.