title: Trigger Factor Reduces the Force Exerted on the Nascent Chain by a Cotranslationally Folding Protein.
abstract: Cotranslational protein folding can generate pulling forces on the nascent chain that can affect the instantaneous translation rate and thereby possibly feed back on the folding process. Such feedback would represent a new way of coupling translation and folding, different from coupling based on, for example, codon usage. However, to date, we have carried out the experiments used to measure pulling forces generated by cotranslational protein folding either in reconstituted in vitro translation systems lacking chaperones, in ill-defined cell lysates, or in vivo; hence, the effects of chaperones on force generation by folding are unknown. Here, we have studied the cotranslational folding of dihydrofolate reductase (DHFR) in the absence and in the presence of the chaperones trigger factor (TF) and GroEL/ES. DHFR was tethered to the ribosome via a C-terminal linker of varying length, ending with the SecM translational arrest peptide that serves as an intrinsic force sensor reporting on the force generated on the nascent chain when DHFR folds. We find that DHFR folds into its native structure only when it has emerged fully outside the ribosome and that TF and GroEL alone substantially reduces the force generated on the nascent chain by the folding of DHFR, while GroEL/ES has no effect. TF therefore weakens the possible coupling between cotranslational folding and translation.
authors.affiliation: Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden.
authors.forename: Ola B
authors.initials: OB
authors.lastname: Nilsson
authors.affiliation: Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden.
authors.forename: Annika
authors.initials: A
authors.lastname: Müller-Lucks
authors.affiliation: Center for Molecular Biology of the University of Heidelberg, German Cancer Research Center, DKFZ-ZMBH Alliance, D-69120 Heidelberg, Germany.
authors.forename: Günter
authors.initials: G
authors.lastname: Kramer
authors.affiliation: Center for Molecular Biology of the University of Heidelberg, German Cancer Research Center, DKFZ-ZMBH Alliance, D-69120 Heidelberg, Germany.
authors.forename: Bernd
authors.initials: B
authors.lastname: Bukau
authors.affiliation: Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden; Science for Life Laboratory, Stockholm University, SE-171 21, Solna, Sweden. Electronic address: gunnar@dbb.su.se.
authors.forename: Gunnar
authors.initials: G
authors.lastname: von Heijne
mesh_terms: D029968:Escherichia coli Proteins / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000378:metabolism; D018832:Molecular Chaperones / Q000378:metabolism; D019696:Peptidylprolyl Isomerase / Q000378:metabolism; D014176:Protein Biosynthesis; D017510:Protein Folding; D013762:Tetrahydrofolate Dehydrogenase / Q000096:biosynthesis*
chemical_list: D029968:Escherichia coli Proteins; C028715:GroE protein, E coli; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D013762:Tetrahydrofolate Dehydrogenase; C403324:trigger factor, E coli; D019696:Peptidylprolyl Isomerase
keywords: GroEL/ES; arrest peptide; chaperone; protein folding; trigger factor