Life of proteins: maturation, translocation, quality control in the cell

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We found an intermediate of GroEL-GroES-assisted protein folding in which substrate protein is tethered to the GroEL's binding sites sharing with GroES. Substrate protein cannot initiate folding in this intermediate until it is release into the cis-cavity. The crystal structure of GroEL-GroES complex with the substrate protein being in cis-cavity. The GroEL ring is deviated from the heptamer symmetry. It was thought that ADP can support chaperonin function but we re-confirmed that only ATP can support folding when ADP was extensively removed from ATP solution.Sup35, an yeast prion protein, forms a prion fiber. We found Hsp 104 and unkown factor contained in the yeast lysate can break the prion fibers. It is ATP dependent. X-ray diffraction of the prion fibers ondicates that beta helix, rather than widely-believed cross-beta, is a plasusible structure of the fiber.ClpB is a chaperon that can disaggregate the heat-denatured proteins in an ATP dependent manner with cooperation with DnaK system. We succeeded in crystal structure analysis of ClpB from thermophilic bacteria. A long alfa-helix beside the two nucleotide binding domains features the structure and mechanistic model of disaggregation was proposed. We also determined crystal structures of ATP-dependent protease, FtsH. Protease domain has hexamer symmetry but ATP-binding domains have three fold symmetry. There is a narrow path to reach protease active site from the outside and ATP-driven open-closed motion seems to provide polypeptide pulling reaction.