Figure 3. Models for −1 programmed frameshifting.

It has been proposed that frameshifting occurs A) during accommodation of aminoacyl tRNA on the third codon of the slippery sequence (‘9 Å’ model); B) after tRNA accommodation but before peptide bond formation (‘simultaneous slippage’ model); C) while tRNAs are in the hybrid state, which coincides with rotation of the small subunit (‘dynamic’ model); D) during eEF2 catalyzed formation of the post translocation state (‘mechanical’ model); E) during tRNA accommodation but with E- and P-site tRNAs in a noncanonical post translocation state. The organization of the figure is adapted from Brierley et al. (22) with the large subunit shown in grey, the small subunit in blue and the slippery mRNA sequence in red.