Key result
Mechanical force generated by nascent chain folding rescues SecM-stalled ribosomes in vivo.
Why the study?
Interactions between the nascent polypeptide and the ribosome exit tunnel regulate protein synthesis rates, but the mechanism of release from SecM-mediated ribosome arrest by mechanical force was unclear.
Mechanical force generated during protein folding can regulate protein synthesis by releasing nascent chain-mediated ribosome arrest.
Force rescues SecM arrest in vitro; leaves open whether mechanical force regulates translation in vivo.
Protein synthesis rates can affect gene expression and the folding and activity of the translation product. Interactions between the nascent polypeptide and the ribosome exit tunnel represent one mode of regulating synthesis rates. The SecM protein arrests its own translation, and release of arrest at the translocon has been proposed to occur by mechanical force. Using optical tweezers, we demonstrate that arrest of SecM-stalled ribosomes can indeed be rescued by force alone and that the force needed to release stalling can be generated in vivo by a nascent chain folding near the ribosome tunnel exit. We formulate a kinetic model describing how a protein can regulate its own synthesis by the force generated during folding, tuning ribosome activity to structure acquisition by a nascent polypeptide.
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Goldman et al. (2015) studied this question. Mechanical force was evaluated on Release of SecM-stalled ribosomes. Mechanical force alone can rescue arrest of SecM-stalled ribosomes, and this force can be generated in vivo by a nascent chain folding near the ribosome tunnel exit.
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