Overall structure of RrQR. a Overall view of RrQR. The protomers are shown in blue, red, orange, and green; NADPH molecules are yellow (left). Side view of RrQR (right). b Stereoview of the structure of the RrQR protomer, presented in light blue. The NADPH molecule is shown as a yellow stick model. c Stereoview of the protomer structure of RrQR, and superimposition with similar structures. RrQR, mannitol 2-dehydrogenase (PDB ID: 1h5q), and trihydroxynaphthalene reductase (PDB ID: 1g0n) are shown in blue, red, and green, respectively. The NADPH molecule of RrQR is shown as a yellow stick model. The α-helices, αA-αG, and the β-strands, βA-βG, are labeled. The αFG between αF and αG is also labeled. The small lobe and variable loop are encircled by dotted lines. The deep cleft is shown by a gray arrow.