Fig. 7: Structural analyses of the ArCuPs and pMMO CuB site showing the Cu site, 2nd-sphere, and outer-sphere interactions.
X-ray structures of 4SCC (A: PDB - 8VHS) and 3SCC (B: PDB - 7L33) show that in 4SCC, the non-coordinating Nδ atoms of His9 make second-sphere H-bond with Glu8 from a neighboring helix, which is involved in extended H2O-mediated H-bonding. The corresponding His residues in 3SCC do not make this H-bond despite having the EH sequence in the heptad. C X-ray structure of K6E/E8K-4SCC (PDB - 9BQR) shows that when Lys and Glu at the 6th and 8th positions are interchanged in the first heptad, the second-sphere H-bond between the His9 and Glu6 plus the H2O-mediated H-bonds are no longer present, which lowers the λH2O. D The CuB site of pMMO (PDB - 7S4H) and its surrounding environment, showing the H-bonding network involving amino acids and solvent, are present. Figures are generated in CCP4mg. The Cu is shown as an orange sphere, and its electron density in A–C is drawn as a red mesh, with the remaining atom density being blue. In these ball-and-stick representations, carbon is green, oxygen is red, and nitrogen is blue. Waters are shown as small red spheres.
