Crystallographic contacts between c14-rings in the crystal lattice. (A) View from the stroma of the chloroplast. C-rings from three neighbor asymmetric units are shown. Positive densities are present between each of two c-rings. (B) View between two c-rings in crystal. Active center (Glu 61) is colored in red. The additional density has two symmetric branches. Each branch contributes to its own C-ring, more likely to the one with the closest Glu 61. (C) View from outside on the c-ring. Two Glu 61 residues are close to the positive density. (Fo – Fc) difference electron density maps are shown at 3.4σ.