title: Chaperone binding at the ribosomal exit tunnel.
abstract: The exit tunnel region of the ribosome is well established as a focal point for interaction between the components that guide the fate of nascent polypeptides. One of these, the chaperone trigger factor (TF), associates with the 50S ribosomal subunit through its N-terminal domain. Targeting of TF to ribosomes is crucial to achieve its remarkable efficiency in protein folding. A similar tight coupling to translation is found in signal recognition particle (SRP)-dependent protein translocation. Here, we report crystal structures of the E. coli TF ribosome binding domain. TF is structurally related to the Hsp33 chaperone but has a prominent ribosome anchor located as a tip of the molecule. This tip includes the previously established unique TF signature motif. Comparison reveals that this feature is not found in SRP structures. We identify a conserved helical kink as a hallmark of the TF structure that is most likely critical to ensure ribosome association.
authors.affiliation: Structural Biology, Department of Medicinal Chemistry, The Danish University of Pharmaceutical Sciences, Universitetsparken 2, DK-2100 Copenhagen, Denmark. ok@dfh.dk
authors.forename: Ole
authors.initials: O
authors.lastname: Kristensen
authors.forename: Michael
authors.initials: M
authors.lastname: Gajhede
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D018360:Crystallography, X-Ray; D019281:Dimerization; D004926:Escherichia coli / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019696:Peptidylprolyl Isomerase / Q000737:chemistry*; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D012270:Ribosomes / Q000737:chemistry*; D017386:Sequence Homology, Amino Acid; D018271:Signal Recognition Particle / Q000737:chemistry
chemical_list: D029968:Escherichia coli Proteins; D018271:Signal Recognition Particle; C403324:trigger factor, E coli; D019696:Peptidylprolyl Isomerase