Figure 6. Critical residues of AtACO2 involved in binding to POA and 2-PA.

(a) Detailed molecular interactions between POA and AtACO2. AtACO2 residues involved in POA binding are shown and labelled. POA is shown as sticks, and its carbon atoms are coloured in yellow. The Zn²⁺ and water molecule are shown as green and magenta spheres, respectively. Salt bridge and hydrogen bond interactions are shown as dashed lines. (b) Molecular interaction between 2-PA and ACO2, depicted as in a. (c) The binding between POA and the AtACO2 mutants were measured using ITC in the presence of Zn²⁺. All mutants display impaired or abolished binding to POA. (d) AtACO2 mutants also display impaired or abolished binding to 2-PA. N.D., not determined.