Subcellular localization and in vivo oxidation-reduction kinetics of thiol peroxidase in Escherichia coli.

Peroxiredoxins are a class of peroxide-scavenging enzymes having a conserved cysteine residue(s) in their active centers. Thiol peroxidase (Tpx) is one of the peroxiredoxins identified in Escherichia coli. Despite the absence of the N-terminal signal sequence for transport across the membrane, it has been characterized as a periplasmic protein. Reanalysis of Tpx localization, using active site cysteine mutants of thioredoxin 1 (Trx1), demonstrated that Tpx forms a mixed-disulfide complex with cytoplasmic Trx1, indicating that Tpx localizes in the cytoplasm.