Abstract
In chloroplasts, thioredoxin (Trx) regulates various enzymes including ATP synthase and the four Calvin cycle enzymes, via thiol-disulfide exchange reaction. This regulation system is known as thiol modulation. Two Trxs, named Trx-m and Trx-f, in chloroplasts function for this redox regulation. On the process of the reduction of the target protein, a reduced form Trx exchanges the disulfide bond and di-thiols with the target thus gives the reduced form targets. Recently we reported a new method to capture possible targets using mutant Trx-immobilized resin, and identified a number of new targets for the chloroplast Trx.
Within these candidates as Trx targets, we identified cyclophilin. In the present study, we characterized the relationship between the redox states of cyclophilin, and the change of the enzyme activity. Trx could reduce a disulfide bond on cyclophilin and regulate the peptidyl-prolyl cis-trans isomerase activity. We now attempt to characterize redox-responsive cysteine residues on the protein.
