Figure 4. A. Alignment of H8-L -H9 sequences from 13 bacterial GluRSs with known crystal structures. Each sequence is annotated with pdb ID, bacterial species (three-letter KEGG code), and structure (“>>t ” and “t<< ” denotes towards and away from tRNA, respectively). The sequence logo on the top represents first four sequences, for which inter-residue hydrophobic/aromatic (black solid lines) and H-bond (red broken line) interactions are shown (see panel B for details). B. Structural superposition of H8-L -H9 motifs in first four proteobacterial GluRSs in panel A. All side-chains that participate in inter-residue interactions shown in panel A are shown as stick model (residue numberings correspond toEco -GluRS).