Site-directed psbA mutants at the tyrosine Y112 position have been generated in Synechocystis PCC6803 cells. The mutation Y112F does not affect photosystem II (PSII) activity as compared with control 4Δ1K cells. However, the Y112L mutant exhibits a photosynthetically impaired phenotype. PSII activity is not detectable in this mutant when grown at 30 μmol photons m-2 s-1, 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 μmol m-2 s-1). The recombination of the Q(B)-/S2,3 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/Q(B)- occurs at 20°C as compared to 35-40°C for the wild-type cells, indicating a possible change in the S2,3/Y(z) 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 Y112 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.
|Original language||American English|
|Number of pages||7|
|Journal||Journal of Photochemistry and Photobiology B: Biology|
|State||Published - Feb 1999|
Bibliographical noteFunding Information:
This work was supported by HFSP, by a grant from the Israel Science Foundation, administered by the Israel Academy of Sciences and Humanities, awarded to I.O. and by the Israel Academy of Sciences and Humanities grant 696/94 (the Scheuer Research Foundation) awarded to J.H.
- Photosystem II
- Site-directed mutagenesis