Nascent Chains: Folding and Chaperone Interaction during Elongation on Ribosomes

• Published in: Philosophical transactions of the Royal Society of London. Series B. Biological sciences 1995-04, Vol.348 (1323), p.89-95
• Main Authors: Tokatlidis, Kostas, Friguet, Bertrand, Deville-Bonne, Dominique, Baleux, Francoise, Fedorov, Alexey N., Navon, Amiel, Djavadi-Ohaniance, Lisa, Goldberg, Michel E.
• Format: Article
• Language: English
• Subjects: Antibodies; Antibodies, Monoclonal - chemistry; Bacteriophage P22 - chemistry; Catalysts and Chaperones; Centrifugation; Epitope Mapping; Epitopes; Escherichia coli - chemistry; Gels; Glycoside Hydrolases - chemistry; Glycoside Hydrolases - immunology; Kinetics; Messenger RNA; Molecular Chaperones - chemistry; Monoclonal antibodies; Peptide Chain Elongation, Translational; Protein Folding; Proteins; Radioactive decay; Ribosomes; Ribosomes - metabolism; Tryptophan Synthase - chemistry; Tryptophan Synthase - immunology; Viral Proteins - chemistry; Viral Proteins - immunology; Viral Tail Proteins
• ISSN: 0962-8436; 1471-2970
• DOI: 10.1098/rstb.1995.0049

Monoclonal antibodies that detect folding intermediates in vitro were used to monitor the appearance of folded polypeptide chains during their synthesis on the ribosomes. Nascent immunoreactive chains of the bacteriophage P22 tail-spike protein and of the Escherichia coli $\beta _{2}$ subunit of tryptophan-synthase were thus identified, suggesting that they can fold on the ribosomes. Moreover, the immunoreactivity of ribosome-bound tryptophan-synthase $\beta $-chains of intermediate lengths was shown to appear with no detectable delay compared to their synthesis. This suggested that $\beta $-chains start folding during their elongation on the ribosomes. However, newly synthesized incomplete $\beta $-chains were shown to interact with chaperones while still bound to the ribosome. Because of the peculiar properties of the epitope recognized by the antitryptophan-synthase monoclonal antibody used, it could not be concluded whether the immunoreactivity of the nascent $\beta $-chains resulted from their ability to fold cotranslationally or from their association with chaperones which might maintain them in an unfolded, immunoreactive state.