Characterization of DNA processing protein A (DprA) of the radiation-resistant bacterium Deinococcus radiodurans

The uptake of environmental DNA (eDNA) by certain bacteria and its integration into their genome creates genetic diversity and new phenotypes. A DNA processing protein A (DprA) is part of a multiprotein complex and facilitate natural transformation (NT) phenotype in most bacteria. The Deinococcus radiodurans, an extremely radioresistant bacterium, is efficient in N T, and its genome encodes nearly all the components of the natural competence complex. Here, we have characterized the DprA of this bacterium (DrDprA) for the known characteristics of DprA proteins in other bacteria and the mechanisms underlying its roles in the transformation of eDNA into the bacterial genome. DrDprA is found to be a unique domain organization implicating some unique functions compared with DprA of other bacteria. In vitro studies showed that the purified recombinant DrDprA binds to both ssDNA and dsDNA with nearly equal affinity and protects ssDNA from nucleolytic degradation. DrDprA showed a strong interaction with DrRecA indicating its role in RecA catalyzed functions in vivo. Mutational studies identified amino acid residues responsible for its oligomerization, interaction with DrRecA, and DNA binding characteristics of DrDprA. Further, we demonstrated that both oligomerization and DNA binding properties of DrDprA are integral to its support in DrRecA catalyzed strand exchange reaction (SER) in vitro. These results suggested that DrDprA is largely structurally conserved with DprA homologs but showed some unique structure-function features like additional domain, the same affinity to ss/ds DNA and both oligomerization and DNA binding domains collectively contribute to its support in DrRecA functions.