Characterization of a newly discovered putative DNA replication initiator from Paenibacillus polymyxa phage phiBP

The bacteriophage phiBP contains a newly discovered putative replisome organizer, a helicase loader, and a beta clamp, which together may serve to replicate its DNA. Bioinformatics analysis of the phiBP replisome organizer sequence showed that it belongs to a recently identified family of putative initiator proteins. We prepared and isolated a wild type-like recombinant protein, gpRO-HC, and a mutant protein gpRO-HCK8A, containing a lysine to alanine substitution at position 8. gpRO-HC had low ATPase activity regardless of the presence of DNA, while the ATPase activity of the mutant was significantly higher. gpRO-HC bound to both single- and double-stranded DNA substrates. Different methods showed that gpRO-HC forms higher oligomers containing about 12 subunits. This work provides the first information about another group of phage initiator proteins, which trigger DNA replication in phages infecting low GC Gram-positive bacteria. [Display omitted] •A newly discovered type of replisome organizer was identified in bacteriophage phiBP.•This protein is composed of two domains and contains an N-terminal winged-helix motif.•Wild type-like recombinant protein gpRO-HC is a weak ATPase.•Amino acid substitution K8A significantly increases the ATPase activity.•gpRO-HC bound to DNA and formed homooligomers with approximately 12 subunits.