4IL6

Structure of Sr-substituted photosystem II

Summary for 4IL6

• Entry DOI: 10.2210/pdb4il6/pdb
• Descriptor: Photosystem Q(B) protein, Photosystem II reaction center protein K, Photosystem II reaction center protein L, ... (40 entities in total)
• Functional Keywords: photosystem ii, electron transfer, light-driven water oxidation, membrane-protein complex, oxygen evolution, oxygen-evolving complex, proton-coupled electron transfer, photosynthesis, reaction centre, sr-substituted photosystem ii, substrate water molecule, trans-membrane alpha helix, electron transport
• Biological source: Thermosynechococcus vulcanus; More
• Total number of polymer chains: 39
• Total formula weight: 719094.02

Authors

Koua, F.H.M.,Umena, Y.,Kawakami, K.,Kamiya, N.,Shen, J.R. (deposition date: 2012-12-29, release date: 2013-03-06, Last modification date: 2023-11-08)

Primary citation

Koua, F.H.,Umena, Y.,Kawakami, K.,Shen, J.R.
Structure of Sr-substituted photosystem II at 2.1 A resolution and its implications in the mechanism of water oxidation
Proc.Natl.Acad.Sci.USA, 110:3889-3894, 2013

PubMed Abstract: Oxygen-evolving complex of photosystem II (PSII) is a tetra-manganese calcium penta-oxygenic cluster (Mn4CaO5) catalyzing light-induced water oxidation through several intermediate states (S-states) by a mechanism that is not fully understood. To elucidate the roles of Ca(2+) in this cluster and the possible location of water substrates in this process, we crystallized Sr(2+)-substituted PSII from Thermosynechococcus vulcanus, analyzed its crystal structure at a resolution of 2.1 Å, and compared it with the 1.9 Å structure of native PSII. Our analysis showed that the position of Sr was moved toward the outside of the cubane structure of the Mn4CaO5-cluster relative to that of Ca(2+), resulting in a general elongation of the bond distances between Sr and its surrounding atoms compared with the corresponding distances in the Ca-containing cluster. In particular, we identified an apparent elongation in the bond distance between Sr and one of the two terminal water ligands of Ca(2+), W3, whereas that of the Sr-W4 distance was not much changed. This result may contribute to the decrease of oxygen evolution upon Sr(2+)-substitution, and suggests a weak binding and rather mobile nature of this particular water molecule (W3), which in turn implies the possible involvement of this water molecule as a substrate in the O-O bond formation. In addition, the PsbY subunit, which was absent in the 1.9 Å structure of native PSII, was found in the Sr-PSII structure.

PubMed: 23426624
DOI: 10.1073/pnas.1219922110

Experimental method

X-RAY DIFFRACTION (2.1 Å)