Binds single-stranded DNA at the primosome assembly site (PAS). During primosome assembly it facilitates the complex formation between PriA and DnaT. Component of the preprimosomal complex composed of one monomer of PriC and DnaT, two monomers of PriA, two dimers of PriB and one hexamer of DnaB. Upon transient interaction with DnaG it forms the primosome. Belongs to the PriB family.