Structural Phylogenomics Retrodicts the Origin of the Genetic Code and Uncovers the Evolutionary Impact of Protein Flexibility
Figure 2
Evolutionary accretion of domains in aaRS enzymes.
The age of domains for aaRS enzymes (arrowheads) were mapped along a timeline of domain appearance generated from a phylogenomic analysis of FF structures in 420 free-living organisms (Figure S1). The three epochs of the protein world are shaded and the evolution of NRPS modules is given as reference together with other relevant landmarks. Domains were identified with concise classification strings [8]. A molecular clock of domain structures places the relative timeline in a geological time scale [13]. The inset shows examples of evolutionary accretion of aaRS domains. Structural models of ProRS from Thermus thermophilus complexed with tRNAPro (PDB entry 1H4S) and LeuRS from Pyrococcus horikoshii complexed with tRNALeu (1WZ2) with catalytic, editing, anticodon-binding and accessory domains colored according to their age of origin.