Abstract
Sensing of light and redox is important in many organisms. Recently, a novel group of flavin-binding domains has been documented as a novel blue light receptor in Euglena gracilis and Rhodobacter sphaeroides (BLUF domain). Similar BLUF-encoding genes are also found in some cyanobacterial genomes. By gene disruption, slr1694 was found to be essential for positive phototaxis in Synechocystis sp. PCC 6803. To further obtain insights into the cyanobacterial BLUF protein, we expressed tll0078 of the thermophilic cyanobacterium Thermosynechococcus elongatus BP-1, which is a homolog of Synechocystis slr1694. His-tagged and non-tagged Tll0078 proteins were purified into homogeneity. They were found to bind an oxidized FAD non-covalently. We made initial efforts to crystallize them and found that the His-tagged one readily aggregated, whereas, the non-tagged protein formed 10 ~ 12 mer of about 160 kDa. We could not observe any spectral changes upon light illumination at the moment.
