Reaction and sequence of DHNA. (A) Reactions catalyzed by DHNA. (B) Chemical structures of NP and MP. (C) Structure-based sequence alignment of Gram-positive SaDHNA [Swiss-Prot:P56740; PDB:2NM3] and Gram-negative EcDHNA [Swiss-Prot:P0AC16; PDB:2O90]. Secondary structural elements are outlined with boxes. The conserved amino acid residues among all DHNA sequences are highlighted in red, while the sequence variations that have significant impact on ligand binding are indicated with arrows in black.