Figure 4.

Average MD structures of first and second position G-U mismatches. (a) First position G-U mismatch with the standard keto form of the anticodon for tRNA^Leu_GAG binding to the UUU codon. (b) Second position G-U mismatch with tRNA^Ser_GGA and the standard keto form of the anticodon. (c) First position mismatch with tRNA^Leu_GAG and the enol form of G36 in the anticodon. (d) Second position mismatch with tRNA^Ser_GGA and the enol form of G35 in the anticodon. The key hydrogen bonds are drawn with dashed lines and the weaker (somewhat longer distances) hydrogen bonds between the anticodon amine and O6 of the codon U are shown as dotted lines in panels (a,b).