The Structure of Photosystem II and the Mechanism of Water Oxidation in Photosynthesis

• Published in: Annual review of plant biology Vol. 66; no. 1; pp. 23 - 48
• Main Author: Shen, Jian-Ren
• Format: Journal Article
• Language: English
• Published: United States Annual Reviews 29.04.2015; Annual Reviews, Inc
• Subjects: Bacteria; Calcium - metabolism; crystal structure; Crystallography; Manganese - metabolism; membrane proteins; Molecular Structure; Oxidation; Oxidation-Reduction; Oxygen; Oxygen - metabolism; oxygen evolution; Photosynthesis; photosystem II; Photosystem II Protein Complex - metabolism; Plants - metabolism; Proteins; S state; Water - metabolism; water splitting; photosystem II; membrane proteins; water splitting; oxygen evolution; photosynthesis; crystal structure; S state
• ISSN: 1543-5008; 1545-2123
• DOI: 10.1146/annurev-arplant-050312-120129

Oxygenic photosynthesis forms the basis of aerobic life on earth by converting light energy into biologically useful chemical energy and by splitting water to generate molecular oxygen. The water-splitting and oxygen-evolving reaction is catalyzed by photosystem II (PSII), a huge, multisubunit membrane-protein complex located in the thylakoid membranes of organisms ranging from cyanobacteria to higher plants. The structure of PSII has been analyzed at 1.9-Å resolution by X-ray crystallography, revealing a clear picture of the Mn 4 CaO 5 cluster, the catalytic center for water oxidation. This article provides an overview of the overall structure of PSII followed by detailed descriptions of the specific structure of the Mn 4 CaO 5 cluster and its surrounding protein environment. Based on the geometric organization of the Mn 4 CaO 5 cluster revealed by the crystallographic analysis, in combination with the results of a vast number of experimental studies involving spectroscopic and other techniques as well as various theoretical studies, the article also discusses possible mechanisms for water splitting that are currently under consideration.