Abstract
In phototrophic organisms, redox sensing is the important mechanism to induce adaptive acclimation of photosynthesis and other functions to changes in various environmental conditions or stresses. We have been studying functional and biochemical roles of cyanobacterial PrxR, SufR, IscR etc by employing functional genomics and DNA microarray techniques. PrxR is the reactive oxygen species (ROS)-responsive repressor that regulates expression of a gene for potent peroxiredoxin Sll1621. PrxR carries four conserved cysteine residues among related proteins of many bacteria. Metal analysis revealed that it retained both zinc and iron. We introduced site-specific mutation in the four cysteine residues and found that any of the conserved residues cannot be replaced without losing iron and DNA binding activity. Redox modification showed that not only the cysteine residues but also iron are critical for regulation of the DNA binding activity. These results suggest that iron-Cys4 complex is the redox-sensing center of PrxR.
