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. 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. Moreover when mutants of Synechocystis that lack ferredoxin-Trx reductase or NADPH-Trx reductase were exposed to high light, the change in transcript level of PedR-target genes was hardly observed. These results suggest that the activity of PedR is regulated by thioredoxin in vivo. We are now trying to identify cysteine residue(s) of PedR interacting with thioredoxin.
