Photosystem II activity and turnover of the D1 protein are impaired in the psbA Y112L mutant of Synechocystis PCC6803 sp.
✍ Scribed by Shlomit Tal; Nir Keren; Joseph Hirschberg; Itzhak Ohad
- Publisher
- Elsevier Science
- Year
- 1999
- Tongue
- English
- Weight
- 646 KB
- Volume
- 48
- Category
- Article
- ISSN
- 1011-1344
No coin nor oath required. For personal study only.
✦ Synopsis
Site-directed psbA mutants at the tyrosine Y 112 position have been generated in Synechocystis PCC6803 cells. The mutation Y 112F does not affect photosystem II (PSII) activity as compared with control 4AIK cells. However, the Y112L mutant exhibits a photosynthetically impaired phenotype. PSII activity is not detectable in this mutant when grown at 30 }xmol photons m 2 s-l, while low levels of the D1 and D2 proteins and oxygen evolution activity are present in the mutant cells grown at a low light intensity (0.5-1 I~mol m 2 s-~). The recombination of the Q8-/S2.s states of PSII in the Y112L mutant cells as detected by thermoluminescence (TL) is altered. The TL signal emission maximum of these cells due to charge recombination of the S2.3/Qa-occurs at 20°C as compared to 35-40°C for the wild-type cells, indicating a possible change in the $23/Y~ equilibrium. The Y112L mutant cells are rapidly photoinactivated and impaired in the recovery of the PSII activity. These results suggest that replacement of the aromatic residue at position Y 112 by a hydrophobic amino acid may alter the function of the donor-side activity and affects the degradation and replacement of the PSII core proteins.