Figure 1. Following translation by a single ribosome on a single mRNA.
(A) Geometry for single-molecule translation experiments. A biotinylated ribosome is loaded onto a single-stranded mRNA and attached to a streptavidin-coated polystyrene bead fixed to a micropipette. The 3′ of the message is anchored to a second bead through a 1460 bp DNA/RNA hybrid handle. Calibrated forces can be applied to the ribosome by manipulating the second bead with an optical trap, while the translation progress of the ribosome is determined by the change in extension of the tether. (B–D) Typical translation events recorded under 4, 6 and 8 pN of constant tension. The upper panels show the codons translated as a function of time, and indicate that translation proceeds not in a continuous manner, but in a series of translational bursts separated by long pauses. The gray line shows the raw (1 kHz) data, while green (translocation) and red (pause) are filtered down to 1 Hz. The lower panels show the instantaneous velocities calculated from the traces above. (E and F) Control experiments, under 8 pN of tension, showing that in the absence of GTP or EF-G, no translation signals were detected.
Figure 1—figure supplement 1. A partial translation trace showing an unusually low noise level, and a sequence of presumptive single-codon translocation steps.
