Fig. 3: Four Watson-Crick base pairs form during +1 frameshifting of tRNAProL.

a A 2.9 Å cryo-EM structure of a ribosomal POST– complex carrying a P/E-configured, unmodified tRNAProL at a CCC-C slippery codon in the +1 frame. b Close-up of the codon-anticodon reveals four Watson-Crick base pairs and an interaction between U38 in the anticodon stem-loop and G+3 in the codon. The additional base pairs are highlighted in gray (and in c). c A schematic of these interactions.