FIGURE 6.

A, comparison of P_II/PipX structures from Anabaena sp. PCC 7120 crystallized in the presence of ADP effector molecules (PDB entry 3N5B) and from S. elongatus (PDB entry 2XG8) in the absence of effector molecules. Orange, P_II from Anabaena sp.; red, P_II from S. elongatus; light green, PipX from Anabaena sp.; dark green, PipX from S. elongatus; ball-and-stick structure, ADP effector molecule in Anabaena sp. structure. B, close-up of A highlighting the T-loop conformations of the two structures. ADP binding of the structure has an influence on the T-loop conformation, whereby the anchoring residues are bent toward the ligand molecule. In the effector-free structure, no additional constrictions are imposed on the conformation.