Fig. 5

Comparison of the acetoin binding sites of S-acting Bdh enzymes. a CgBdh; b KpBdh, and c SmBdh. Carbon backbone are represented in green for CgBdh, cyan for KpBdh and grey for SmBdh. Main chain atoms of the amino acid residues involved in the substrate binding are shown in lines and side chains are shown in sticks. NAD ⁺ substrate is shown in sticks with magenta carbons. (3S)-acetoin in CgBdh is represented in cyan backbone and (3R)-acetoin in KpBdh is represented in purple backbone, are modeled following acetoin binging in SmBdh using C1, C2, C3 and O2 atoms of the acetoin molecules in SmBdh as anchors. Available hydrogen bonds are depicted as yellow dashed lines. Hydrogen bonds specific for (3S)-acetoin O3 atom are depicted as cyan dashed lines (panels a and c). W71 indicates a water molecule