A DNA-binding protein that is part of the type III plasmid partition system used to ensure correct segregation of the pBM400 plasmid. Binds the plasmid origin of replication, probably cooperatively, forming a ring or short helix with external DNA (PubMed:23010931). Its effect on RNA expression has not been shown (Probable). Homodimer. Dimers bind to DNA, forming a protein-bound filament which may form a helix around the TubZ filament.