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ACS Chem Biol. 2008 Sep 19;3(9):555-66. doi: 10.1021/cb800059u. Epub 2008 Aug 22.

Chain dynamics of nascent polypeptides emerging from the ribosome.

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1
Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706, USA.

Abstract

Very little is known about the conformation of polypeptides emerging from the ribosome during protein biosynthesis. Here, we explore the dynamics of ribosome-bound nascent polypeptides and proteins in Escherichia coli by dynamic fluorescence depolarization and assess the population of cotranslationally active chaperones trigger factor (TF) and DnaK. E. coli cell-free technology and fluorophore-linked E. coli Met-tRNA f Met enable selective site-specific labeling of nascent proteins at the N-terminal methionine. For the first time, direct spectroscopic evidence captures the generation of independent nascent chain motions for a single-domain protein emerging from the ribosome (apparent rotational correlation time approximately 5 ns), during the intermediate and late stages of polypeptide elongation. Such motions are detected only for a sequence encoding a globular protein and not for a natively unfolded control, suggesting that the independent nascent chain dynamics may be a signature of folding-competent sequences. In summary, we observe multicomponent, severely rotationally restricted, and strongly chain length/sequence-dependent nascent chain dynamics.

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PMID:
18717565
PMCID:
PMC2572860
DOI:
10.1021/cb800059u
[Indexed for MEDLINE]
Free PMC Article

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