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.Heterohexamer of two PFD-alpha type and four PFD-beta type subunits. Binds to MYC; interacts with its N-terminal domain. Represses the transcriptional activity of MYC.Highly expressed in pancreas and skeletal muscle and moderately in other tissues.Belongs to the prefoldin subunit alpha family.