Specific binding of DnaA to the DnaA box motif in the cyanobacterium Synechococcus elongatus PCC 7942.

In bacterial DNA replication, the initiator protein DnaA binds to the multiple DnaA box sequences located at oriC to facilitate the unwinding of duplex DNA strands. The cyanobacterium Synechococcus elongatus PCC 7942, which contains multiple chromosomal copies per cell, has DnaA box (like sequences around the oriC region, which is located upstream of dnaN. We previously observed the binding of DnaA around the oriC region; however, the DNA-binding specificity of DnaA to DnaA box sequences has not been examined. Here, we analyzed the binding specificity of DnaA protein to the DnaA box in S. elongatus by using bio-layer interferometry (BLI), a method for monitoring intermolecular interactions. We observed that recombinant DnaA protein recognized specifically the DnaA box sequence TTTTCCACA in vitro. In addition, DNA binding activity was significantly increased by R328H mutation of DnaA. This is the first report to characterize DnaA binding to the DnaA box sequence in cyanobacteria.