Fig. 7: SmpB mimics the interactions of a tRNA anticodon loop in the P site.
From: Structures of tmRNA and SmpB as they transit through the ribosome
a Focus on the interactions between SmpB and the 16S rRNA P-site in the translocation state. The cryo-electron density map is displayed and coloured according to the local resolutions as computed with ResMap74. b Same as (a), but without the map. For clarity, cartoon representation is used for SmpB and only His22 and His126 are shown. c Comparison with a P-site tRNA30 (PDB code 7K00). The SmpB C-terminal tail occupies the mRNA path, replacing the codon–anticodon interaction. SmpB also reproduces the anticodon loop interactions with the 16S rRNA. The stacking interaction between His22 and A790 replaces the interaction usually observed with the sugar of tRNA’s nucleotide (nt) 38. Meanwhile, His136 replaces the anticodon’s nucleotide 34, stacking on the C1400 rRNA nucleotide. SmpB is purple, tRNA is green, mRNA is yellow and 16S rRNA is khaki.
