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. Author manuscript; available in PMC: 2018 Apr 30.
Published in final edited form as: Adv Exp Med Biol. 2017;966:103–148. doi: 10.1007/5584_2017_93

Figure 1.

Figure 1

The hypothesis of Rodin and Ohno [43]. A. Schematic of the hypothesis. Genes for Class I and Class II aaRS are aligned in opposite directions as they would be oriented in an ancestral gene bearing the coding sequences on opposite strands. Vertical lines denote the extent of ancestral bi-directional coding, indicated by base-pairing of the coding sequences identified first in the Class-defining motifs in each superfamily. Large domains—the two anticodon-binding domains at the C-terminus of each Class and an insertion domain, ID in Class II, CP1 in Class I—are indicated by boxes and dashed lines, respectively. Substrate binding sites for the amino acid activation reaction, ATP and amino acid, are indicated. B. Summary of published evidence supporting the hypothesis, to be discussed in detail in this review.