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). Required for tubulin stability and spindle and centrosome formation in cooperation with Vhl. Heterohexamer of two PFD-alpha type and four PFD-beta type subunits (By similarity). Interacts with itself. Interacts with Vhl and betaTub56D/tubulin beta-1 chain. Interacts with tubulin alpha-beta heterodimers by itself or in complex with Vhl. Does not interact with microtubules (MTs). Expressed in larval central nervous system (CNS) and pupal testis (at protein level). Pupal lethal. Most mutants die just before emergence from the pupal case. In mutant larval CNS, neuroblasts show bipolar spindles that may lack one or both centrosomes or monopolar spindles having one or two centrosomes at the single pole. The mitotic index is elevated twofold over that in wild-type larval brains and the ratio of metaphase:anaphase two- to threefold over wild-type. Mutant neuroblasts also show a decrease of 25% in betaTub56D/tubulin beta chain-1 expression. Mutant mature primary spermatocytes show impaired MT network resulting in meiotic spindles either absent or highly abnormal. In mutant testis, decreased expression of betaTub85D/tubulin beta-2 chain is observed. Belongs to the prefoldin subunit alpha family.