title: Localization of the trigger factor binding site on the ribosomal 50S subunit.
abstract: In Escherichia coli, protein folding is undertaken by three distinct sets of chaperones, the DnaK-DnaJ and GroEL-GroES systems and the trigger factor (TF). TF has been proposed to be the first chaperone to interact with the nascent polypeptide chain as it emerges from the tunnel of the 70S ribosome and thus probably plays an important role in co-translational protein folding. We have made complexes with deuterated ribosomes (50S subunits and 70S ribosomes) and protated TF and determined the TF binding site on the respective complexes using the neutron scattering technique of spin-contrast variation. Our data suggest that the TF binds in the form of a homodimer. On both the 50S subunit and the 70S ribosome, the TF position is in proximity to the tunnel exit site, near ribosomal proteins L23 and L29, located on the back of the 50S subunit. The positions deviate from one another, such that the position on the 70S ribosome is located slightly further from the tunnel than that determined for the 50S subunit alone. Nevertheless, from both determined positions interaction between TF and a short nascent chain of 57 amino acid residues would be plausible, compatible with a role for TF participation in co-translational protein folding.
authors.affiliation: Max-Planck-Institut für Molekulare Genetik, AG Ribosomen, Ihnestrasse 73, D-14195 Berlin, Germany.
authors.forename: Gregor
authors.initials: G
authors.lastname: Blaha
authors.forename: Daniel N
authors.initials: DN
authors.lastname: Wilson
authors.forename: Gerlind
authors.initials: G
authors.lastname: Stoller
authors.forename: Gunter
authors.initials: G
authors.lastname: Fischer
authors.forename: Regine
authors.initials: R
authors.lastname: Willumeit
authors.forename: Knud H
authors.initials: KH
authors.lastname: Nierhaus
mesh_terms: D001665:Binding Sites; D004926:Escherichia coli / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000378:metabolism*; D009502:Neutrons; D019696:Peptidylprolyl Isomerase / Q000378:metabolism*; D012270:Ribosomes / Q000378:metabolism*; D012542:Scattering, Radiation
chemical_list: D029968:Escherichia coli Proteins; C403324:trigger factor, E coli; D019696:Peptidylprolyl Isomerase