Function of PsbO-Asp158 in photosystem II: effects of mutation of this residue on the binding of PsbO and function of PS
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ORIGINAL ARTICLE
Function of PsbO‑Asp158 in photosystem II: effects of mutation of this residue on the binding of PsbO and function of PSII in Thermosynechococcus vulcanus Qingjun Zhu1,2 · Yanyan Yang1 · Yanan Xiao1,2 · Wenda Wang1,2 · Tingyun Kuang1 · Jian‑Ren Shen1,3 · Guangye Han1 Received: 28 October 2019 / Accepted: 24 January 2020 © Springer Nature B.V. 2020
Abstract PsbO-D158 is a highly conserved residue of the PsbO protein in photosystem II (PSII), and participates in one of the hydrogen-bonding networks connecting the manganese cluster with the lumenal surface. In order to examine the role of PsbO-D158, we mutated it to E, N or K in Thermosynechococcus vulcanus and characterized photosynthetic properties of the mutants obtained. The growth rates of these three mutants were similar to that of the wild type, whereas the oxygen-evolving activity of the three mutant cells decreased to 60–64% of the wild type. Fluorescence kinetics showed that the mutations did not affect the electron transfer from QA to QB, but slightly affected the donor side of PSII. Moreover, all of the three mutant cells were more sensitive to high light and became slower to recover from photoinhibition. In the isolated thylakoid membranes from the three mutants, the PsbU subunit was lost and the oxygen-evolving activity was reduced to a lower level compared to that in the respective cells. PSII complexes isolated from these mutants showed no oxygen-evolving activity, which was found to be due to large or complete loss of PsbO, PsbV and PsbU during the process of purification. Moreover, PSII cores purified from the three mutants contained Psb27, an assembly co-factor of PSII. These results suggest that PsbOD158 is required for the proper binding of the three extrinsic proteins to PSII and plays an important role in maintaining the optimal oxygen-evolving activity, and its mutation caused incomplete assembly of the PSII complex. Keywords PsbO · Site-directed mutagenesis · Photosystem II · Oxygen evolution · Thermosynechococcus vulcanus Abbreviations BN-PAGE Blue native polyacrylamide gel electrophoresis CmR Chloramphenicol-resistant gene Qingjun Zhu and Yanyan Yang have contributed equally to this work. * Jian‑Ren Shen [email protected]‑u.ac.jp * Guangye Han [email protected] 1
Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, No. 20, Nanxincun, Xiangshan, Beijing 100093, China
2
University of Chinese Academy of Sciences, Yuquan Rd, Shijingshan District, Beijing 100049, China
3
Research Institute for Interdisciplinary Science, Graduate School of Natural Science and Technology, Okayama University, Tsushima Naka 3‑1‑1, Okayama 700‑8530, Japan
Chl Chlorophyll DCBQ 2,6-Dichloro-p-benzoquinone DCMU 3-(3,4-Dichlorophenyl)-1,1-dimethylurea DDM N-Dodecyl-β-d-maltoside MSP Manganese-stabilizing protein OEC Oxygen-evolving complex PCR Polymerase chain reaction PSII Photosystem II WT Wild type
Introduction In oxygenic photosynthesis, light-driven water
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