title: Co-translational binding of GroEL to nascent polypeptides is followed by post-translational encapsulation by GroES to mediate protein folding.
abstract: The eubacterial chaperonins GroEL and GroES are essential chaperones and primarily assist protein folding in the cell. Although the molecular mechanism of the GroEL system has been examined previously, the mechanism by which GroEL and GroES assist folding of nascent polypeptides during translation is still poorly understood. We previously demonstrated a co-translational involvement of the Escherichia coli GroEL in folding of newly synthesized polypeptides using a reconstituted cell-free translation system (Ying, B. W., Taguchi, H., Kondo, M., and Ueda, T. (2005) J. Biol. Chem. 280, 12035-12040). Employing the same system here, we further characterized the mechanism by which GroEL assists folding of translated proteins via encapsulation into the GroEL-GroES cavity. The stable co-translational association between GroEL and the newly synthesized polypeptide is dependent on the length of the nascent chain. Furthermore, GroES is capable of interacting with the GroEL-nascent peptide-ribosome complex, and experiments using a single-ring variant of GroEL clearly indicate that GroES association occurs only at the trans-ring, not the cis-ring, of GroEL. GroEL holds the nascent chain on the ribosome in a polypeptide length-dependent manner and post-translationally encapsulates the polypeptide using the GroES cap to accomplish the chaperonin-mediated folding process.
authors.affiliation: Department of Medical Genome Sciences, Graduate School of Frontier Sciences, The University of Tokyo, FSB-401, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8562.
authors.forename: Bei-Wen
authors.initials: BW
authors.lastname: Ying
authors.affiliation: Department of Medical Genome Sciences, Graduate School of Frontier Sciences, The University of Tokyo, FSB-401, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8562; Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency, 4-1-8 Honcho Kawaguchi, Saitama, 332-0012, Japan. Electronic address: taguchi@k.u-tokyo.ac.jp.
authors.forename: Hideki
authors.initials: H
authors.lastname: Taguchi
authors.affiliation: Department of Medical Genome Sciences, Graduate School of Frontier Sciences, The University of Tokyo, FSB-401, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8562. Electronic address: ueda@k.u-tokyo.ac.jp.
authors.forename: Takuya
authors.initials: T
authors.lastname: Ueda
mesh_terms: D002474:Cell-Free System; D018835:Chaperonin 10 / Q000378:metabolism*; D018834:Chaperonin 60 / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000378:metabolism; D018832:Molecular Chaperones / Q000378:metabolism; D010455:Peptides / Q000737:chemistry*; D011485:Protein Binding; D014176:Protein Biosynthesis; D017510:Protein Folding; D012270:Ribosomes
chemical_list: D018835:Chaperonin 10; D018834:Chaperonin 60; D029968:Escherichia coli Proteins; D018832:Molecular Chaperones; D010455:Peptides