4DP6: The 1.67 Angstrom crystal structure of reduced (CuI) poplar plastocyanin B at pH 8.0

Plastocyanin (PC) from poplar leaves is present in two isoforms, PCa and PCb, which differ in sequence by amino acid replacements at locations remote from the copper center and simultaneously act in the photosynthetic electron-transport chain. We describe ultra-high resolution structures of PCa and high-resolution structures of PCb, both under oxidizing and reducing conditions at pH 4, 6 and 8. The docking on cytochrome f and photosystem I, respectively, has been modeled for both isoforms. PCa and PCb exhibit closely similar overall and active-site structures, except for a difference in the relative orientation of the acidic patches. The isoforms exhibit substantial differences in the dependence of the reduced (Cu(I)) geometry on pH. In PCa, the decrease in pH causes a gradual dissociation of His87 from Cu(I) at low pH, probably adopting a neutral tautomeric state. In PCb, the histidine remains covalently bound to Cu(I) and may adopt a doubly protonated state at low pH. The fact that both isoforms have similar although not identical functions in photosynthetic electron flows suggests that the His87 imidazole does not play a crucial role for the pathway of electron transport from cytochrome f to oxidized PC.
PDB ID: 4DP6Download
MMDB ID: 107562
PDB Deposition Date: 2012/2/13
Updated in MMDB: 2017/11
Experimental Method:
x-ray diffraction
Resolution: 1.67  Å
Source Organism:
Similar Structures:
Biological Unit for 4DP6: monomeric; determined by author and by software (PISA)
Molecular Components in 4DP6
Label Count Molecule
Protein (1 molecule)
Plastocyanin B, Chloroplastic
Molecule annotation
Chemicals (2 molecules)
* Click molecule labels to explore molecular sequence information.

Citing MMDB