title: Structure and dynamics of a ribosome-bound nascent chain by NMR spectroscopy.
abstract: Protein folding in living cells is inherently coupled to protein synthesis and chain elongation. There is considerable evidence that some nascent chains fold into their native structures in a cotranslational manner before release from the ribosome, but, despite its importance, a detailed description of such a process at the atomic level remains elusive. We show here at a residue-specific level that a nascent protein chain can reach its native tertiary structure on the ribosome. By generating translation-arrested ribosomes in which the newly synthesized polypeptide chain is selectively (13)C/(15)N-labeled, we observe, using ultrafast NMR techniques, a large number of resonances of a ribosome-bound nascent chain complex corresponding to a pair of C-terminally truncated immunoglobulin (Ig) domains. Analysis of these spectra reveals that the nascent chain adopts a structure in which a native-like N-terminal Ig domain is tethered to the ribosome by a largely unfolded and highly flexible C-terminal domain. Selective broadening of resonances for a group of residues that are colocalized in the structure demonstrates that there are specific but transient interactions between the ribosome and the N-terminal region of the folded Ig domain. These findings represent a step toward a detailed structural understanding of the cellular processes of cotranslational folding.
authors.affiliation: Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom.
authors.forename: Shang-Te Danny
authors.initials: ST
authors.lastname: Hsu
authors.forename: Paola
authors.initials: P
authors.lastname: Fucini
authors.forename: Lisa D
authors.initials: LD
authors.lastname: Cabrita
authors.forename: Hélène
authors.initials: H
authors.lastname: Launay
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Dobson
authors.forename: John
authors.initials: J
authors.lastname: Christodoulou
mesh_terms: D002247:Carbon Isotopes / Q000737:chemistry; D004247:DNA / Q000737:chemistry; D006801:Humans; D007136:Immunoglobulins / Q000737:chemistry / Q000235:genetics; D007553:Isotope Labeling; D009587:Nitrogen Isotopes / Q000737:chemistry; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000737:chemistry* / Q000235:genetics; D012333:RNA, Messenger / Q000737:chemistry; D012270:Ribosomes / Q000737:chemistry*
chemical_list: D002247:Carbon Isotopes; D007136:Immunoglobulins; D009587:Nitrogen Isotopes; D011506:Proteins; D012333:RNA, Messenger; D004247:DNA