Molecular chaperones are key players in proteostasis, the balance between protein synthesis, folding, assembly and degradation. They are helped by a plethora of cofactors termed cochaperones, which direct chaperones towards any of these different, sometime opposite pathways. One of these is prefoldin (PFD), present in eukaryotes and in archaea, a heterohexamer whose best known role is the assistance to group II chaperonins (the Hsp60 chaperones found in archaea and the eukaryotic cytosolic) in the folding of proteins in the cytosol, in particular cytoskeletal proteins. However, over the last years it has become evident a more complex role for this cochaperone, as it can adopt different oligomeric structures, form complexes with other proteins and be involved in many other processes, both in the cytosol and in the nucleus, different from folding. This review intends to describe the structure and the many functions of this interesting macromolecular complex.
Keywords: CCT; Chaperonin; Cochaperone; Electron microscopy; Group II chaperonin; Molecular chaperone; Prefoldin; Protein folding; TRiC; Thermosome; X-ray crystallography.