Structural Phylogenomics Retrodicts the Origin of the Genetic Code and Uncovers the Evolutionary Impact of Protein Flexibility
Figure 3
Coevolution of aaRS domains and cognate tRNA.
A. The ages of catalytic and editing domain FFs (ndFF) interacting with type II tRNA (Group 1) and type I tRNA (Group 2) and the age of anticodon-binding domain FFs (Group 3; provided only as reference) were plotted against the age of tRNA isoacceptors (Saac). The significant correlation (P<0.0067) unfolds an evolutionary timeline of early domain function. The time period spanning the most ancient functions (class I TyrRS) and the most recent trans-editing function (Ala-X of AlaRS) involves ∼2 Gy of evolution. B. Coevolution of anticodon-specific tRNAs (Scod) and anticodon-binding domain FFs (ndFF) is significant for the early start of the code (dashed line; F = 20.8; P<0.001), but are followed by episodes of tRNA structural recruitment. An ‘idealized’ timeline partitions code expansions in three age groups (A, B and C).