期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2017
卷号：114
期号：45
页码：12063-12068
DOI：10.1073/pnas.1713343114
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：The cytochrome (cyt) b 6 f complex and Stt7 kinase regulate the antenna sizes of photosystems I and II through state transitions, which are mediated by a reversible phosphorylation of light harvesting complexes II, depending on the redox state of the plastoquinone pool. When the pool is reduced, the cyt b 6 f activates the Stt7 kinase through a mechanism that is still poorly understood. After random mutagenesis of the chloroplast petD gene, coding for subunit IV of the cyt b 6 f complex, and complementation of a Δ petD host strain by chloroplast transformation, we screened for impaired state transitions in vivo by chlorophyll fluorescence imaging. We show that residues Asn122, Tyr124, and Arg125 in the stromal loop linking helices F and G of cyt b 6 f subunit IV are crucial for state transitions. In vitro reconstitution experiments with purified cyt b 6 f and recombinant Stt7 kinase domain show that cyt b 6 f enhances Stt7 autophosphorylation and that the Arg125 residue is directly involved in this process. The peripheral stromal structure of the cyt b 6 f complex had, until now, no reported function. Evidence is now provided of a direct interaction with Stt7 on the stromal side of the membrane.
关键词：cytochrome b 6 f complex ; structure–function ; random mutagenesis ; Stt7 kinase ; state transitions
