The cyanobacterial cell division factor Ftn6 contains an N-terminal DnaD-like domain

In this study, we identified an as yet undescribed domain located in the conserved N-terminal region of Ftn6. This 77 amino-acids-long domain, designated here as FND (Ftn6 N-Terminal Domain), exhibits striking sequence and structural similarities with the DNA-interacting module, listed in the PFAM database as the DnaD-like domain (pfam04271). We took advantage of the sequence similarities between FND and the DnaD-like domains to construct a homology 3D-model of the Ftn6 FND domain from the model cyanobacterium Synechocystis PCC6803. Mapping of the conserved residues exposed onto the FND surface allowed us to identify a highly conserved area that could be engaged in Ftn6-specific interactions.Overall, similarities between FND and DnaD-like domains as well as previously reported observations on Ftn6 suggest that FND may function as a DNA-interacting module thereby providing an as yet missing link between DNA replication and cell division in cyanobacteria. Consistently, we also showed that Ftn6 is involved in tolerance to DNA damages generated by UV rays.DNA replication and cell division are probably the most fundamental processes in the cell life cycle. Both proceed through a remarkably conserved general mechanism and are inextricably intertwined to each others and to the cell metabolism [1].The DNA replication cycle can be divided into three distinct stages; initiation, elongation, and termination. Replication is initiated by the highly conserved AAA+ superfamily ATPase-member DnaA that binds the oriC, inducing DNA strand melting [2-4]. In E. coli, DnaA also interacts with the ring helicase DnaB and directs the loading of DnaB/DnaC onto the single stranded DNA (ssDNA) region. After binding of DnaB on the ssDNA region of the oriC, DnaC is released in an ATPase dependent manner. Then, DnaB recruits the DnaG primase and DNA polymerase III to form the replication fork [4]. In B. subtilis, two additional essential proteins, called DnaB (be aware of the confusing nomenclat