Fig. 5. Hydrogen bond networks in cupredoxins. The scheme highlights the intricate hydrogen bond networks involving the first and second coordination spheres. (A) AcoP (PDB: 7Z3B). (B) Rusticyanin (PDB: 2CAK). (C) Azurin (PDB: 4AZU). (D) Pseudoazurin (PDB: 8PAZ). Amino acids within the first coordination sphere (copper ligands) are represented by their one-letter code followed by the sequence position number. Amino acids within the second coordination sphere are represented only by the sequence position number, coloured in purple, red or orange to represent further distance (degree of indirect hydrogen bonding) to copper ligands. The same colour scheme is used for bridging water molecules that participate to the network (purple, red or orange circles). Blue lines encompass domains connected through backbone. No further search was pursued from residues (orange) that were three hydrogen bonds away from copper ligands. Hydrogen bonds (2.5–3.2 Å, black lines) were used to identify network amino acids. Double and triple lines represent respectively two or three independent H-bonds between two amino acids. For the first coordination sphere only, also weak hydrogen bonds (3.2–4.4 Å) are traced (dashed lines). No further search was pursued on residues connected through weak hydrogen bonds only. Blue shapes group together residues that are connected through backbone.