Stimulates the DNA unwinding activity of PriA helicase, which does not seem to require single-stranded DNA-binding by PriB. Activates DNA-dependent ATP hydrolysis catalyzed by PriA (PubMed:21861872). Has a weak single-stranded DNA-binding activity (PubMed:21861872, PubMed:19906704). Binds weakly also double-stranded DNA, a partial duplex DNA with a 3' single-stranded DNA overhang, and a forked DNA structure with fully duplex leading and lagging strand arms in vitro (PubMed:21861872). Homodimer (PubMed:19906704). Component of the preprimosomal complex (By similarity). Interacts with PriA with high affinity, independent of DNA presence (PubMed:21861872, PubMed:19906704). Belongs to the PriB family.