Apr 17, 2012

Extended protein/water H-bond networks in photosynthetic water oxidation

Biochimica Et Biophysica Acta
Ana-Nicoleta Bondar, H Dau

Abstract

Oxidation of water molecules in the photosystem II (PSII) protein complex proceeds at the manganese-calcium complex, which is buried deeply in the lumenal part of PSII. Understanding the PSII function requires knowledge of the intricate coupling between the water-oxidation chemistry and the dynamic proton management by the PSII protein matrix. Here we assess the structural basis for long-distance proton transfer in the interior of PSII and for proton management at its surface. Using the recent high-resolution crystal structure of PSII, we investigate prominent hydrogen-bonded networks of the lumenal side of PSII. This analysis leads to the identification of clusters of polar groups and hydrogen-bonded networks consisting of amino acid residues and water molecules. We suggest that long-distance proton transfer and conformational coupling is facilitated by hydrogen-bonded networks that often involve more than one protein subunit. Proton-storing Asp/Glu dyads, such as the D1-E65/D2-E312 dyad connected to a complex water-wire network, may be particularly important for coupling protonation states to the protein conformation. Clusters of carboxylic amino acids could participate in proton management at the lumenal surface of PSII. We ...Continue Reading

Mentioned in this Paper

Molecular Dynamics
Biochemical Pathway
Cytochrome C Oxidase
Translocon Complex
Electrolytes
Bacteriorhodopsins
Thylakoid Membrane
Entire Lumen of Body System
Calcium
Stroma

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