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Proc Natl Acad Sci U S A. 2018 Nov 27;115(48):12206-12211. doi: 10.1073/pnas.1810517115. Epub 2018 Nov 8.

A small single-domain protein folds through the same pathway on and off the ribosome.

Author information

1
Institute for Quantitative Biosciences (QB3), University of California, Berkeley, CA 94720.
2
Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892.
3
Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720.
4
Institute for Quantitative Biosciences (QB3), University of California, Berkeley, CA 94720; marqusee@berkeley.edu.
5
Department of Chemistry, University of California, Berkeley, CA 94720.

Abstract

In vivo, proteins fold and function in a complex environment subject to many stresses that can modulate a protein's energy landscape. One aspect of the environment pertinent to protein folding is the ribosome, since proteins have the opportunity to fold while still bound to the ribosome during translation. We use a combination of force and chemical denaturant (chemomechanical unfolding), as well as point mutations, to characterize the folding mechanism of the src SH3 domain both as a stalled ribosome nascent chain and free in solution. Our results indicate that src SH3 folds through the same pathway on and off the ribosome. Molecular simulations also indicate that the ribosome does not affect the folding pathway for this small protein. Taken together, we conclude that the ribosome does not alter the folding mechanism of this small protein. These results, if general, suggest the ribosome may exert a bigger influence on the folding of multidomain proteins or protein domains that can partially fold before the entire domain sequence is outside the ribosome exit tunnel.

KEYWORDS:

cotranslational folding; optical tweezers; protein folding; ribosome; single-molecule force spectroscopy

PMID:
30409803
PMCID:
PMC6275501
DOI:
10.1073/pnas.1810517115
[Indexed for MEDLINE]
Free PMC Article

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