Figure 4: The A·A mismatch in the decoding centre of the 70S ribosome.
From: Structural insights into the translational infidelity mechanism
The left panels demonstrate the A·A mismatch at the first (a) and second (b) positions of the codon–anticodon duplexes. As for the C·A mismatches, A1493 (a) and A1492 with G530 (b) in 16S rRNA constrain the sugar-phosphate backbones of the first and second mispairs by hydrogen bonding. In a, the exact position of the codon adenosine was not detectable and the figure shows one of the possible positions of this nucleobase; in b, the distances between adenosines exceed 3.6 Å demonstrating absence of strong interactions. In a and b, the right panels depict overall geometry of the mismatches in the codon–anticodon mini-helices.
