What is β-carotene doing in the photosystem II reaction centre?

Alison Telfer, G. W. Brudvig, T. A. Moore, S. Styring, A. W. Rutherford, P. Fromme, E. M. Aro

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147 Citations (Scopus)

Abstract

During photosynthesis carotenoids normally serve as antenna pigments, transferring singlet excitation energy to chlorophyll, and preventing singlet oxygen production from chlorophyll triplet states, by rapid spin exchange and decay of the carotenoid triplet to the ground state. The presence of two β-carotene molecules in the photosystem II reaction centre (RC) now seems well established, but they do not quench the triplet state of the primary electron-donor chlorophylls, which are known as P680. The β-carotenes cannot be close enough to P680 for triplet quenching because that would also allow extremely fast electron transfer from β-carotene to P680+, preventing the oxidation of water. Their transfer of excitation energy to chlorophyll, though not very efficient, indicates close proximity to the chlorophylls ligated by histidine 118 towards the periphery of the two main RC polypeptides. The primary function of the β-carotenes is probably the quenching of singlet oxygen produced after charge recombination to the triplet state of P680. Only when electron donation from water is disturbed does β-carotene become oxidized. One β-carotene can mediate cyclic electron transfer via cytochrome b559. The other is probably destroyed upon oxidation, which might trigger a breakdown of the polypeptide that binds the cofactors that carry out charge separation.

Original languageEnglish
Pages (from-to)1431-1440
Number of pages10
JournalPhilosophical Transactions of the Royal Society B: Biological Sciences
Volume357
Issue number1426
DOIs
Publication statusPublished - Oct 29 2002

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Keywords

  • Photoinhibition
  • Photosystem II
  • Singlet oxygen
  • Triplet state
  • β-carotene

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)
  • Agricultural and Biological Sciences(all)

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