title: Identification of nascent chain interaction sites on trigger factor.
abstract: The role of ribosome-binding molecular chaperones in protein folding is not yet well understood. Trigger factor (TF) is the first chaperone to interact with nascent polypeptides as they emerge from the bacterial ribosome. It binds to the ribosome as a monomer but forms dimers in free solution. Based on recent crystal structures, TF has an elongated shape, with the peptidyl-prolyl-cis/trans-isomerase (PPIase) domain and the N-terminal ribosome binding domain positioned at opposite ends of the molecule and the C-terminal domain, which forms two arms, positioned in between. By using site specifically labeled TF proteins, we have demonstrated that all three domains of TF interact with nascent chains during translation. Interactions with the PPIase domain were length-dependent but independent of PPIase activity. Interestingly, with free TF, these same sites were found to be involved in forming the dimer interface, suggesting that dimerization partially occludes TF-nascent chain binding sites. Our data indicate the existence of two regions on TF along which nascent chains can interact, the NC-domains as the main site and the PPIase domain as an auxiliary site.
authors.affiliation: Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, D-82152 Martinsried, Germany.
authors.forename: Sathish K
authors.initials: SK
authors.lastname: Lakshmipathy
authors.forename: Sladjana
authors.initials: S
authors.lastname: Tomic
authors.forename: Christian M
authors.initials: CM
authors.lastname: Kaiser
authors.forename: Hung-Chun
authors.initials: HC
authors.lastname: Chang
authors.forename: Pierre
authors.initials: P
authors.lastname: Genevaux
authors.forename: Costa
authors.initials: C
authors.lastname: Georgopoulos
authors.forename: José M
authors.initials: JM
authors.lastname: Barral
authors.forename: Arthur E
authors.initials: AE
authors.lastname: Johnson
authors.forename: F Ulrich
authors.initials: FU
authors.lastname: Hartl
authors.forename: Stephanie A
authors.initials: SA
authors.lastname: Etchells
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry*; D002460:Cell Line; D019281:Dimerization; D019286:Endopeptidase K / Q000737:chemistry; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000502:physiology*; D008027:Light; D008958:Models, Molecular; D009154:Mutation; D019696:Peptidylprolyl Isomerase / Q000737:chemistry* / Q000502:physiology*; D010957:Plasmids / Q000378:metabolism; D014176:Protein Biosynthesis; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D012270:Ribosomes / Q000737:chemistry*
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D019286:Endopeptidase K; C403324:trigger factor, E coli; D019696:Peptidylprolyl Isomerase