Watching single ribosome translation in real time: a quantitative study of ribosome helicase activity
March 7, 2012 - 10:00am
The ribosome translates the genetic information encoded in messenger RNA into protein. Folded structures in the coding region of an mRNA represent
a kinetic barrier that lowers the peptide elongation rate, as the ribosome must disrupt structures it encounters in the mRNA to allow translocation to the next codon. Such structures are exploited by the cell to create diverse strategies for translation regulation. Although strand separation activity is inherent to the ribosome, requiring no exogenous helicases, its mechanism is still unknown. By using a single-molecule optical tweezers assay to follow in real time the codon-by-codon translation of mRNA hairpins, we conducted a quantitative characterization of the effect of the RNA structural stability on the peptide elongation rate, which revealed distinct mechanisms utilized by the ribosome to unwind mRNA structures. Our results establish a quantitative mechanical basis for understanding the mechanism of translational regulation of the elongation rate by structured mRNAs.