Peptide-chain elongation during protein synthesis entails sequential aminoacyl-tRNA selection and translocation reactions that proceed rapidly (2-20 per second) and with a low error rate (around 10 -3 to 10 -5 at each step) over thousands of cycles 1 . The cadence and fidelity of ribosome transit through mRNA templates in discrete codon increments is a paradigm for movement in biological systems that must hold for diverse mRNA and tRNA substrates across domains of life. Here we use single-molecule fluorescence methods to guide the capture of structures of early translocation events on the bacterial ribosome. Our findings reveal that the bacterial GTPase elongation factor G specifically engages spontaneously achieved ribosome conformations while in an active, GTP-bound conformation to unlock and initiate peptidyl-tRNA translocation. These findings suggest that processes intrinsic to the pre-translocation ribosome complex can regulate the rate of protein synthesis, and that energy expenditure is used later in the translocation mechanism than previously proposed.
Organizational Affiliation:
Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, USA.
EB [auth 16] IE [auth 23] JE [auth 23] KE [auth 23] LE [auth 23]
EB [auth 16], IE [auth 23], JE [auth 23], KE [auth 23], LE [auth 23], ME [auth 23], NE [auth 23], OE [auth 23], PE [auth 23], QE [auth 23], RE [auth 23]
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