Plastocyanins poplar

Plastocyanin (poplar) Cull, pH 6.0 His37 1.91 Cys87 2.07 His87 2.82 Met92 2.81 0.36 IPLC 34... 

Bai, Y W., Chung, J., Dyson, H. J., and Wright, P. E. (2001). Structural and dynamic characterization of an unfolded state of poplar apo-plastocyanin formed under nondenaturing conditions. Protein Sci. 10, 1056-1066. 

A solution structure of French Bean plastocyanin has been reported by Wright and co-workers,19 using nuclear magnetic resonance techniques described in Section 3.5 of Chapter 3. The structure, determined from a plastocyanin molecule in solution rather than in a solid-state crystal, agrees well with that of reduced poplar plastocyanin X-ray crystallographic structure reported above. Conformations of protein side chains constituting the hydrophobic core of the French bean plastocyanin are well-defined by the NMR technique. Surface side chains show... 

Figure 14.1 (Left) X-ray structure of plastocyanin from poplar leaves as a ribbon diagram with the metal ion and its ligands highlighted, PDB code 1PLC (right) Type 1 Cu site in Cu(II)-nitrite reductase from Alcaligenes faecalis, PDB code 1AS6. (From Messerschmidt et al., 2001. Reproduced with permission from John Wiley Sons., Inc.)...

Figure 30 X-Ray structure of the active site of poplar plastocyanin...

It is interesting to note that the plastocyanin from the alga Anabaena variabilis has a similar structure to that isolated from poplar, while having a different amino acid sequence.58 This results in an overall positive charge of +2. Thus, as shown in Figure 32a, it affords a wellshaped response for the Cu(II)/Cu(I) reduction E° = + 0.32 V vs. NHE) using a perpendicular pyrolytic graphite electrode, without the presence of additives. 

Fig. 1. The a-carbon chain structure of poplar plastocyanin [16] including details of the active site and the remote acidic patches 42-45 and 59-61. The first of these has been modified to include an acidic residue at position 45 as e.g. for spinach and French bean plastocyanins...

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... 

Fig. 5. The a-carbon chain of poplar plastocyanin residues 50-64 from the X-ray crystal structure thin line), compared with that of S. obliquus plastocyanin obtained from a 2DNMR study [37a], showing the effect of deletions of residues 57 and 58...

Parsley, spinach, French bean, poplar and S. obliquus (but not A. variabilis) conform extensively to the above criteria for reaction at the remote site. There is extensive evidence for cytochrome f reacting at the remote site on plastocyanin. The aromatic residue at 83 would seem to be a prime candidate as lead-in group for electron transfer. Desolvation at the surface around 83, and interaction with an aromatic component on the reaction partner, e.g. the porphyrin ring of cytochrome f, may be important. The exact manner of electron transfer has yet to be confirmed. The distance from the aromatic ring of Tyr83 to the Cu for electron transfer is 12 A. 

The blue, or type 1, copper proteins, azurin from Pseudomonas aeruginosa (Adman et ai, 1978 Adman and Jensen, 1981) and from Al-caligenes denitrificans (Norris et al., 1983, 1986) and poplar plastocyanin (Guss and Freeman, 1983 Guss et al., 1986), have been studied by X-ray diffraction. These involve a Cu(I)/Cu(II) redox system. Cu(I) d ) is... 

A qualitative understanding of these features was provided in 1978 when the crystal structure of poplar leaf plastocyanin and Pseudomonas aeruginosa azurin appear-ed 2,73) proteins appears to be coordinated by two histidines with... 

Additional information has been obtained from single crystal, polarized optical and ESR spectroscopic studies924 on poplar plastocyanin, which have allowed a correlation of the electronic structure of the blue copper active site with its geometric structure. In summary, the three dominant absorption bands at 13 350, 16 490 and 17 870 cm-1 were assigned to CysS- Cu (d 2-,2 charge-transfer transitions. The methionine makes only a small contribution, due to the long Cu—S(Met) bond (2.9 A) and the poor overlap of the methionine sulfur orbitals with the dx y orbital of copper. Histidine-Cu charge transfer contributes to the weaker absorptions at 21 390 and... 

Fig. 5-9. The copper site in poplar plastocyanin based on the structure determined by Guss and Freeman (1983). Some of the bond angles and all of the copper-ligand bond distances are indicated.

Fig. 5-11. The effect of pH at the Cu(I) site in poplar plastocyanin as determined by Guss et al. (1986). Bond distances are shown in Angstroms and residue numbers are indicated in parentheses.

Figure 3. Blue copper proteins. A X-ray structure of poplar plastocyanin (21). B Absorption spectrum of plastocyanin and normal D 4 cCuCl42 (e scale expanded by 10). C X-band EPR spectrum of plastocyanin and Y>4 cCuCl42. ...

Figure 4. Single-crystal EPR of poplar plastocyanin (29) orientation of the dxz.y2 orbital. A Unit cell and molecular orientation with respect to the applied magnetic field. B EPR spectra and simulations for the crystal orientations shown. C Orientation of the g direction and the dx2.yz orbital superimposed on the blue copper site.

Figure 6. X-ray absorption spectroscopy. A Energy level diagram depicting a Cu Is - HOMO transition at 8979 eV. B Orientation averaged XAS spectra. C Polarized single-crystal XAS spectra for poplar plastocyanin. (Data are from reference 35.)...

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