Abstract
Oxidative stress and its protection are critical for survival of oxygenic phototrophs. We have demonstrated that superoxide stress induced expression of iron-sulfur center assembly genes in the sufB operon via a putative transcriptional repressor sll0088(SufR), which possesses an iron-sulfur center motif. Here we studied the SufR homolog protein of Thermosynechococcus elongatus BP-1(TeSufR), which was expressed in E. coli . When TeSufR was prepared anaerobically, it showed [4Fe-4S]-type EPR signals. When TeSufR was prepared aerobically, it showed a [1Fe-0S]-type EPR signal. We also reconstituted the TeSufR apoprotein in vitro with iron under reducing conditions. We obtained similarly [4Fe-4S]-type TeSufR under anaerobic conditions, and [1Fe-0S]-type TeSufR under aerobic conditions. Further exposure of TeSufR to the aerobic solution revealed that [4Fe-4S]-type is more labile than [1Fe-0S]-type. Possible role and its physiological relevance of these two iron-sulfur centers will be discussed.
