Binds specifically to cytosolic chaperonin (c-CPN) and transfers target proteins to it. Binds to nascent polypeptide chain and promotes folding in an environment in which there are many competing pathways for nonnative proteins (By similarity). Has a role in gonadogenesis. Heterohexamer of two PFD-alpha type and four PFD-beta type subunits. Expressed in the distal cell tip of developing embryos. Worms exhibit defects in distal cell tip migration during gonadogenesis, reduced microtubule growth rate in embryos, and larvae arrest and lethality. Belongs to the prefoldin subunit beta family.