Molecular functional characterization of Trx-h7 in Arabidopsis

Thioredoxin (Trx) functions as a disulfide reductase, regulating the redox state of proteins. Arabidopsis Trx-h types are classified into three subgroups based on their N-terminal extension region and lipid modifications. Not all Trx-h type functions have been fully unraveled. In this study, the molecular functions of Trx-h7 were studied. Trx-h7 contains the redox-active site motif WCGPC and consists of 129 amino acids. To investigate the molecular functions of the Trx-h7, we measured its insulin reductase activity, holdase chaperone activity, and DNA-binding activity. The insulin reductase activity of Trx-h7 was significantly lower than that of Trx-h2 but increased with increasing Trx-h7 protein concentration. Like Trx-h2, Trx-h7 showed no holdase chaperone activity. Trx-h7 had low binding affinity for single-stranded DNA, but high binding affinity for double-stranded DNA. These results indicate that Trx-h7, as a disulfide reductase, regulates the redox status of its target protein and binds to dsDNA.