Evolution of mistranslation rate.

<p>(A) Mutations in the variable arm of the tS(AGA)D3 serine tRNAs. The variable arm mutated in three lines independently (lines 6, 9, and 10). The identity elements for the SerRS are indicated in red (discriminator base G73 and the GC base pairs in the variable arm). Structure of the molecule was predicted by tRNAscan-SE analysis. (B) Evolution of mistranslation rate. The figure shows β-galactosidase enzyme activities in the ancestor and evolved lines, all of which carry the mistranslation causing tRNA_CAG^Ser construct. The ancestor is isogenic to the wild type, with the only exception being that the latter carries an empty vector instead of tRNA_CAG^Ser. Enzyme activities were normalized to the enzyme activity measured in wild-type control carrying no tRNA_CAG^Ser by normalization to the total amount of β-galactosidase protein (quantified by western blot). The bars indicate mean ± 95% confidence interval. Mann-Whitney U test was used to assess difference in fitness between ancestor and evolved lines. **/*** indicates <i>p</i> < 0.01/0.001, respectively. (C) β-galactosidase enzyme activities in the ancestor and the evolved lines carrying no tRNA_CAG^Ser. Enzyme activities were normalized to the enzyme activity measured in the wild type after normalization to the total amount of β-galactosidase protein quantified using western blot. The bars indicate mean ± 95% confidence interval. Mann-Whitney U test was used to assess difference in fitness between ancestor and evolved lines */** indicates <i>p</i> < 0.05/0.01, respectively.