Thioredoxin peroxidase is a member of peroxiredoxin (Prx) family, which uses a thioredoxin (Trx) as an immediate electron donor for the reduction of peroxide. We have identified C-terminal truncated TPx from Schizosaccharomyces pombe and also have found the truncated form is significantly tenacious against the inactivation of H2O2 than the intact form. Peroxidase assay of a series of recombinant C-terminal truncation mutants (Δ192, Δ191, Δ188, Δ184, Δ176, and Δ165) revealed that TPx could be inactivated (Δ192), reactivated (Δ191-Δ176) and reinactivated (Δ165) by serial truncation from C-terminus. We did not find any significant kinetic difference among reactivated forms; however, distinctive loss of affinity to H2O2 (Km = 5 μM) than that of the intact form (< <5 μM, undeterminable) was monitored. Characterization of a series of Lys191 point mutants manifested that the loss of affinity caused by a deprivation of positive charge born in Lys191 and the loss of affinity resulted in the resistibility to H2O2. Disk inhibition assay with S. pombe cells overexpressing wild-type, Δ192 and Δ191 mutants evidenced that the truncated forms functioning in vitro as well as in vivo.
Bibliographical noteFunding Information:
This work was supported in part by a grant 971-0506-036-2 and 1999-2-202-002-5 from the KOSEF, and by a grant from the Hormone Research Center (HRC) of Chonnam National University. We thank Drs. K. S. Kwon and S. E. Ryu for the valuable discussions about the crystal structures of peroxiredoxins.
All Science Journal Classification (ASJC) codes
- Molecular Biology