Two functionally distinct manganese clusters formed by introducing a mutation in the carboxyl terminus of a photosystem II reaction center polypeptide, D1, of the green alga Chlamydomonas reinhardtii

Aya Hatano-Iwasaki, Jun Minagawa, Yorinao Inoue, Yuichiro Takahashi

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

To study the function of the carboxyl-terminal domain of a photosystem II (PSII) reaction center polypeptide, D1, chloroplast mutants of the green alga Chlamydomonas reinhardtii have been generated in which Leu-343 and Ala-344 have been simultaneously or individually replaced by Phe and Ser, respectively. The mutants carrying these replacements individually, L343F and A344S, showed a wild-type phenotype. In contrast, the double mutant, L343FA344S, evolved O2 at only 20-30% of the wild-type rate and was unable to grow photosynthetically. In this mutant, PSII accumulated to 60% of the wild-type level, indicating that the O2-evolving activity per PSII was reduced to approximately half that of the wild-type. However, the amount of Mn atom detected in the thylakoids suggested that a normal amount of Mn cluster was assembled. An investigation of the kinetics of flash-induced fluorescence yield decay revealed that the electron transfer from Q-A to QB was not affected. When a back electron transfer from Q-A to a donor component was measured in the presence of 3-(3,4-dichlorophenol)-1,1-dimethylurea, a significantly slower component of the Q-A oxidation was detected in addition to the normal component that corresponds to the back electron transfer from the Q-A to the S2-state of the Mn cluster. Thermoluminescence measurements revealed that L343FA344S cells contained two functionally distinct Mn clusters. One was equivalent to that of the wild-type, while the other was incapable of water oxidation and was able to advance the transition from the S1-state to the S2-state. These results suggested that a fraction of the Mn cluster had been impaired by the L343FA344S mutation, leading to decreased O2 evolution. We concluded that the structure of the C-terminus of D1 is critical for the formation of the Mn cluster that is capable of water oxidation, in particular, transition to higher S-states.

Original languageEnglish
Pages (from-to)299-310
Number of pages12
JournalBiochimica et Biophysica Acta - Bioenergetics
Volume1504
Issue number2-3
DOIs
Publication statusPublished - Apr 2 2001

Keywords

  • Chlamydomonas reinhardtii
  • Chloroplast transformation
  • Manganese cluster
  • O evolution
  • Photosystem II
  • psbA

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Cell Biology

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