Abstract
Thioredoxin (Trx) localized in stroma, is reduced by ferredoxin and ferredoxin-thioredoxin reductase. The required reducing equivalents are provided by photosynthetic electron transfer system. Reduced form Trx activates various thiol-enzymes in stroma by way of reduction and directly supplies reducing equivalents required for the reaction cycle of peroxiredoxin as well, which functions as detoxification system of reactive oxygen species. In addition, we showed that stroma Trx functions as a part of a trans-membrane reducing equivalent transfer system in higher plant chloroplasts. HCF164 that is a membrane anchored thioredoxin-like protein faced to thylakoid lumen side, receives reducing equivalents from stroma Trx. In this study, we analyzed the membrane protein CcdA, a candidate component of this reducing equivalents transfer system itself. We discuss the electron transfer mechanism across the thylakoid membranes.
