| Mutation of Residue Arginine^18 of Cytochrome b559 α-Subunit and its Effects on Photosystem Ⅱ Activities in Chlamydomonas reinhardtii |
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| 作者姓名： | Jing-Jing Ma Liang-Bi Li Yu-Xiang Jing Ting-Yun Kuang |
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| 作者单位： | [1]Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences Beijing 100093, China [2]Graduate University of Chinese Academy of Sciences, Beijing 100049, China |
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| 基金项目： | Supported by the National Natural Science Foundation of China （30370849）.
The authors thank EH Harris （Duke University, Durham, NC, USA） for the gift of C. reinhardtii WT strain CC-125 mt^＋, plasmid p78 and pUC-atpX-AAD. Antiserum for the α-subunit of Cyt b559 was kindly provided by J Barber （Imperial College of Science, Technology and Medicine, London, UK）, and anti-Psb0 and anti-LHCII were provided by Li-Xin Zhang （Institute of Botany, Chinese Academy of Sciences, Beijing, China）. |
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| 摘 要： | It has been known that arginine is used as the basic amino acid in the α-subunit of cytochrome bsss （Cyt bsss） except histidine. However, previous studies have focused on the function of histidine in the activities of photosystem （PS） Ⅱ and there are no reports regarding the structural and/or functional roles of arginine in PSll complexes. In the present study, two arginine18 （R18） mutants of Chlamydomonas reinhardtii were constructed using site-directed mutagenesis, in which R18 was replaced by glutamic acid （E） and glycine （G）. The results show that the oxygen evolution of the PSII complex in the R18G and R18E mutants was approximately 60% of wild-type （WT） levels and that, after irradiation at high light intensity, oxygen evolution for the PSll of mutants was reduced to zero compared with 40% in WT cells. The efficiency of light capture by PSll （Fv/Fm） of R18G and R18E mutants was approximately 42%-46% that of WT cells. Furthermore, levels of the α-subunit of Cyt bsss and PsbO proteins were reduced in thylakoid membranes compared with WT. Overall, these data suggest that R18 plays a significant role in helping Cyt bss9 maintain the structure of the PSll complex and its activity, although it is not directly bound to the heme group.
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| 关 键 词： | 衣滴虫 叶绿体转换 细胞色素 光合体系 |
| 修稿时间： | 2006-08-072006-12-11 |
Mutation of Residue Arginine18 of Cytochrome b559α-Subunit and its Effects on Photosystem II Activities in Chlamydomonas reinhardtii |
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| Authors: | Jing-Jing Ma Liang-Bi Li Yu-Xiang Jing Ting-Yun Kuang |
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| Institution: | ( Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China;;Graduate University of Chinese Academy of Sciences, Beijing 100049, China;) |
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| Abstract: | It has been known that arginine is used as the basic amino acid in the α‐subunit of cytochrome b559 (Cyt b559) except histidine. However, previous studies have focused on the function of histidine in the activities of photosystem (PS) II and there are no reports regarding the structural and/or functional roles of arginine in PSII complexes. In the present study, two arginine18 (R18) mutants of Chlamydomonas reinhardtii were constructed using site‐directed mutagenesis, in which R18 was replaced by glutamic acid (E) and glycine (G). The results show that the oxygen evolution of the PSII complex in the R18G and R18E mutants was approximately 60% of wild‐type (WT) levels and that, after irradiation at high light intensity, oxygen evolution for the PSII of mutants was reduced to zero compared with 40% in WT cells. The efficiency of light capture by PSII (Fv/Fm) of R18G and R18E mutants was approximately 42%–46% that of WT cells. Furthermore, levels of the α‐subunit of Cyt b559 and PsbO proteins were reduced in thylakoid membranes compared with WT. Overall, these data suggest that R18 plays a significant role in helping Cyt b559 maintain the structure of the PSII complex and its activity, although it is not directly bound to the heme group. |
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| Keywords: | Chlamydomonas reinhardtii chloroplast transformation cytochrome b559 mutation photosystem II |
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