Figure 3. Putative evolutionary pathway of the Candida albicans tRNACAGSer. In silico studies suggested that insertion of an adenosine in the middle position of the anticodon of a tRNACGASer gene transformed the 5′-CGA-3′ into a 5′-CAG-3′ anticodon, originating the Ser tRNA mutant 1, which is capable of decoding Leu CUG as Ser. Decoding accuracy and efficiency requires two other mutations, namely G37 (mutant 2) and G33 (mutant 3). The second mutation permitted the recognition of the tRNACAGSer by the LeuRS in addition to its cognate SerRS, which introduced ambiguity at CUG codons, while the third mutation lowered leucylation efficiency of the tRNACAGSer.