WcbI binds to coenzyme A. (a) Electron-density map showing the binding of coenzyme A (CoA) to WcbI. WcbI is shown as a cyan cartoon, with CoA as sticks. For clarity, water molecules are not shown. An Fo − Fc OMIT map is shown contoured at 3σ. The bond from CoA to Cys14 is shown. (b) Schematic drawing of the WcbI–CoA interactions. (c) Key WcbI–CoA interactions. WcbI is shown as a cyan cartoon, with interacting side chains as purple sticks. CoA is shown as sticks. Hydrogen-bond distances are shown. Nitrogen, blue; oxygen, red, phosphorus, orange; CoA carbon, yellow; WcbI carbon, purple. (a) and (c) were prepared with the PyMOL Molecular Graphics System (Schrödinger) and (b) was prepared with LigPlot+ (Laskowski & Swindells, 2011).