Fig. 3.

A near-cognate codon−anticodon interaction in ${\text{tRNA}}_{\text{GGC}}^{\text{Ala}}$ influences the stability of the A32−U38 pair. (A) Zoomed-in view of the interaction between the anticodon stem−loop of ${\text{tRNA}}_{\text{GGC}}^{\text{Ala}}$ with a near-cognate GCA codon. G₊₄-C36 and C₊₅-G35 form Watson–Crick base pairs; a A₊₆•G34 mismatch forms at the third or wobble position. (B) Two hydrogen bonds form between the cis Watson–Crick A₊₆•G34 interaction. (C) The A32−U38 pair is destabilized in a structure of the 70S bound to ${\text{tRNA}}_{\text{GGC}}^{\text{Ala}}$ in the A site decoding a near-cognate GCA codon. The 2F_O−F_C electron density map (gray mesh) is contoured at 1.0σ.