PprA interacts with replication proteins and affects their physicochemical properties required for replication initiation in Deinococcus radiodurans

The deletion mutant of pprA, a gene encoding pleiotropic functions in radioresistant bacterium Deinococcus radiodurans, showed an increased genomic content and ploidy in chromosome I and chromosome II. We identified oriC in chromosome I (oriCI) and demonstrated the sequence specific interaction of deinococcal DnaA (drDnaA) with oriCI. drDnaA and drDnaB showed ATPase activity while drDnaB catalyzed 5'[->]3' dsDNA helicase activity. These proteins showed both homotypic and heterotypic interactions. The roles of C-terminal domain of drDnaA in oriCI binding and its stimulation of ATPase activity were demonstrated. Notably, PprA showed ~2 times higher affinity to drDnaA as compared to drDnaB and attenuated both homotypic and heterotypic interactions of these proteins. Interestingly, the ATPase activity of drDnaA but not drDnaB was inhibited in presence of PprA. These results suggested that PprA influences the physicochemical properties of drDnaA and drDnaB that are required for initiation of DNA replication at oriCI site in this bacterium.