Journal Article

Quality Control of Photosystem II

Yasusi Yamamoto

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 42, issue 2, pages 121-128
Published in print February 2001 | ISSN: 0032-0781
Published online February 2001 | e-ISSN: 1471-9053 | DOI:
Quality Control of Photosystem II

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  • Biochemistry
  • Molecular and Cell Biology
  • Plant Sciences and Forestry


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Photosystem II is particularly vulnerable to excess light. When illuminated with strong visible light, the reaction center D1 protein is damaged by reactive oxygen molecules or by endogenous cationic radicals generated by photochemical reactions, which is followed by proteolytic degradation of the damaged D1 protein. Homologs of prokaryotic proteases, such as ClpP, FtsH and DegP, have been identified in chloroplasts, and participation of the thylakoid-bound FtsH in the secondary degradation steps of the photodamaged D1 protein has been suggested. We found that cross-linking of the D1 protein with the D2 protein, the α-subunit of cytochrome b559, and the antenna chlorophyll-binding protein CP43, occurs in parallel with the degradation of the D1 protein during the illumination of intact chloroplasts, thylakoids and photosystem II-enriched membranes. The cross-linked products are then digested by a stromal protease(s). These results indicate that the degradation of the photodamaged D1 protein proceeds through membrane-bound proteases and stromal proteases. Moreover, a 33-kDa subunit of oxygen-evolving complex (OEC), bound to the lumen side of photosystem II, regulates the formation of the cross-linked products of the D1 protein in donor-side photoinhibition of photosystem II. Thus, various proteases and protein components in different compartments in chloroplasts are implicated in the efficient turnover of the D1 protein, thus contributing to the control of the quality of photosystem II under light stress conditions.

Keywords: Key words: D1 protein — OEC subunits — Photosystem II — Protease — Protein degradation — Reactive oxygen species.; Abbreviations: CP43, antenna-chlorophyll-binding protein of photosystem II having a relative molecular mass of 43 kDa; D1 and D2, reaction center-binding proteins of photosystem II; FT-IR, Fourier transform infrared; OEC33, -24 and -18, extrinsic proteins of the oxygen-evolving complex having relative molecular masses of 33, 24 and 18 kDa, respectively; P680, primary electron donor of photosystem II; QA and QB, primary and secondary plastoquinone electron acceptors of photosystem II, respectively; TyrZ and TyrD, redox-active tyrosines of the D1 and D2 proteins, respectively.

Journal Article.  6005 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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