Fig. 5.

A schematized view of a single translocation cycle of translation that shows three possible points in the cycle that −1 frameshifting could potentially be stimulated by a downstream pseudoknot. In one scenario, −1 PRF is proposed to occur from the hybrid A/P-P/E state which is stabilized by EF-G·GTP (eEF2·GTP) binding; this binding in turn, weakens the interaction of the deacylated P-site tRNA with the mRNA inducing frameshifting before 30S (40S in eukaryotes) translocation to the classical P/P and E/E states accompanied by hydrolysis and EF-G·GDP (eEF2·GDP) release (Ermolenko et al., 2007, Spiegel et al., 2007). Alternatively, −1 PRF occurs during the 30S (40S) translocation step itself (Namy et al., 2006). Both models are distinguished from a previous model that invoked simultaneous slippage (SS) of two tRNAs in the 5′ direction after accommodation and before peptidyl transfer (Jacks et al., 1988, Plant et al., 2003). See text for additional details.