Figure 6.

Arginyl-tRNA synthetase phylogenetic motifs at the three PSZ thresholds are highlighted. Residues colored red indicate phylogenetic motifs identified using the (A) -2.04, (B) -2.93, and (C) -3.26 PSZ thresholds, which correspond to gap ranges of {-1.0: -2.0}, {-1.0, -2.5}, and {-1.0, -3.0}, respectively. The arginine substrate is colored yellow; the tRNA is colored blue; and the anticodon is color cyan. Using (A), two structurally unique clusters of phylogenetic motifs are identified. One corresponds to the enzyme active site, whereas the other corresponds to three H-bonds between the enzyme and the anti-codon arm of tRNA. (D) is the same (A), but with the rest of the enzyme removed for clarity.