Elucidating the Molecular Mechanism of Dynamic Photodamage of Photosystem II Membrane Protein Complex by Integrated Proteomics Strategy

Photosystem II (PSII), as a multiple-subunit chloroplast membrane-associated pigment-protein complex on the thylakoid membrane, is a primary target of light-induced photodamage. However, the overall molecular details of the conformation and composition dynamics of PSII photodamage are still controversial. In this study, we investigated systematically the dynamic conformation, degradation, and oxidation processes of PSII photodamage by integrating chemical cross-linking and top-down proteomics strategies. The dynamic disassembly of the PSII complex, as well as the degradation fragments from both extrinsic and intrinsic protein PSII subunits, were feasibly probed during the loss of O2 -evolving activity. Some long-term controversial issues, including the activity loss of PSII complex occurs before the detachment of the Mn4CaO5 cluster, were clarified. Finally, a detailed route map of dynamic PSII photodamage was outlined at the molecular level for the first time, which markedly enhanced our understanding of the molecular mechanism of photodamage.