NDK structure. (A) Cartoon representation of LbNDK protomer, showing secondary structure elements labeled according to the nomenclature proposed by Morera et al. . Colors are used to highlight important regions: Kpn loop (orange), Head (yellow), C-terminal extension (purple) and dimer/trimer interfaces (red). (B) Cartoon representation of LbNDK subunit, colored according to the B-factor values, from blue (lowest) to red (highest). (C) Electrostatic surface representation colored by charge from red (negative) to blue (positive) generated using the PyMOL Charge-smoothed potential approach. Inside the highly positive active site cleft, a phosphate ion (stick representation) is bounded to Lys11, Asn114 and the conserved residue His117.