Figure 4.

Comparison of the similarity of the double beta hairpin cores of (A) the bacterial CCA adding enzyme head domain and (B) the class II tRNA synthetase minimum core of the catalytic domain. The minimum catalytic domains are in dark gray. Note the beta hairpin components 3 and 2 in (B), which define the motif II loop; and 1 and 2 in (A), which contain the two Aspartic acids. The strand numbering for (B) is as in reference [11] for the entire traditionally-defined class II catalytic domain.