Abstract
In cyanobacteria, small transcriptional regulators that consist solely of a helix-turn-helix motif of LuxR type are highly conserved. These regulators possess three cysteine residues in their C terminal region. In Synechocystis sp. PCC 6803, a small LuxR-type regulator, PedR, regulates the expression of several high-light responsive genes when the activity of photosynthetic electron transport is low. Amino acid substitution in PedR revealed that Cys80 is essential for dimerization. But amino acid residues involved in redox sensing were not identified by this experiment. In order to identify regulatory factors interacting with PedR, pull down analysis was performed. We detected the interaction of thioredoxin with PedR and confirmed that purified thioredoxin reduced PedR effectively. This suggests that PedR is inactivated when reducing equivalents were supplied by thioredoxin in vivo. We are now trying to identify cysteine residues interacting with thioredoxin.
