Plastocyanin backbone

Fig. 3. (a) Copper site in plastocyanin. (b) Ribbon drawing of the plastocyanin backbone, (c and d) Schematic of plastocyanin topology. 

The solution conformation of plastocyanin from French bean, spinach, and S. obliquus has now been determined from distance and dihedral angle constraints derived by NMR spectroscopy [37,40]. These two-dimensional NMR studies have indicated a well defined backbone conformation, which is very similar to that of poplar PCu in the crystalline state. However, in the case of S. obliquus there are deletions at positions S7 and 58 which influence the shape in the acidic region and in particular close to residues 59-61. The gap which is created is in effect repaired with consequent tightening of the loop 57-62 as indicated in Fig. 5. One of the pronounced bulges at the remote site of poplar and presumably other higher plant plastocyanins is not therefore present in S. obliquus (or plastocyanin from other green algae) [31, 32], as well as parsley... 

Cylinders and barrels. The twisted P sheets of proteins are often curved to form structures known as P cylinders or p barrels (Fig. 2-16).113 114 Simple cylinders formed by parallel P strands form the backbones of the electron transport protein plastocyanin, the enzyme superoxide dismutase, the oxygen carrier... 

Bertini I, Bryant DA, Ciurli S, Dikiy A, Fernandez CO, Luchi-nat C, Safarov N, Vila AJ, Zhao JD. Backbone dynamics of plastocyanin in both oxidation states - Solution structure of the reduced form and comparison with the oxidized state. J. Biol. Chem. 2001 276 47217-47226. 

The system is defined by the oxidation state of the copper ion (Cu), the protein (Pc red, reduced plastocyanin Pc ox, oxidised plastocyanin CBP, cucumber basic protein Nir, nitrite reductase Vacuum, quantum chemical optimisation in vacuum [14,34] Crystal, range observed in the available crystal structures in the Brookhaven protein data bank), and whether there is a connection between the metal ligands and the protein backbone (Con). 

Single-crystal structural data have provided valuable information about blue copper proteins containing Type 1 Cu centres. Figure 28.10a shows a representation of the folded protein chain of spinach plastocyanin. The Cu(II) centre lies within a pocket in the chain, bound by a Cys, a Met and two His residues (Figure 28.10b) the S(Met) atom is significantly further away from the Cu(II) centre than is S(Cys). Figure 28.10c shows the backbone of the protein chain in azurin isolated from the bacterium Pseudomonas putida. The coordination environment of the Cu(II) centre resembles that in plastocyanin with Cu—S(Met) > Cu—S(Cys), but in addition, an O atom from an adjacent Gly residue is involved in a weak coordinate interaction (Figure 28.10d). Structural... 

O Fig. 28.10 The structure of spinach plastocyanin (a) the backbone of the protein chain showing the position of the Cu(II) centre and (b) the coordination sphere of the Cu(II) centre, consisting of one methionine, one cysteine and two histidine residues. The structure of azurin from Pseudomonas putida (c) the backbone of the protein chain showing the position of the Cu(II) centre and (d) the Cu(II) centre, coordinated by a methionine, a cysteine and two histidine residues one O atom from the glycine residue adjacent to one of the histidines interacts weakly with the metal centre (the red hashed line). Hydrogen atoms are omitted colour code Cu, brown S, yellow C, grey N, blue O, red. 

Extensive structural information has been obtained for plastocyanins from plants and algae (58, 81). In general, as pictured in Fig. 11 (57), the copper atom is located at one end of the protein in a hydrophobic pocket formed by loops in the peptide backbone. The higher plant plastocyanins have two histidines, His-37 and His-87, both of which coordinate to copper. Cys-84 and Met-92 serve as the other Cu ligands. 

---