Prefoldin

Prefoldin is one family of chaperone proteins found in the domains of eukarya and archaea. Prefoldin acts in combination with other molecules to promote protein folding in cells where there are many other competing pathways for folding. Chaperone proteins perform non-covalent assembly of other polypeptide-containing structures in vivo. They are implicated in the folding of most other proteins. In archaea, prefoldins are believed to function in combination with group II chaperonins in de novo protein folding. In eukarya however, prefoldins have acquired a more specific function: they are used to establish correct tubular assembly for many tubular proteins, such as actin. Actin accounts for 5-10% of all protein found in eukaryotic cells, which therefore means that prefoldin is quite prevalent in the cells. Actin is made of two strings of beads wound round each other and is one of the three main parts of the cytoskeleton of eukaryotic cells. Prefoldin bonds specifically to cytosolic chaperonin protein. This complex of prefoldin and chaperonin then forms molecules of actin in the cytosol. The prefoldin acts as a transporter molecule that transports bound, unfolded target proteins to the chaperonin (C-CPN) molecule.