Characterization of carotenoid and chlorophyll photooxidation in photosystem II.
Characterization of carotenoid and chlorophyll photooxidation in photosystem II.
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光系统 II 中类胡萝卜素和叶绿素光氧化的表征。
DOI：
10.1021/bi001992o
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发表时间：
2001
期刊：
影响因子：
2.9
通讯作者：
Brudvig,GW
中科院分区：
文献类型：
--
作者：
Tracewell,CA;Cua,A;Stewart,DH;Bocian,DF;Brudvig,GW
光系统II（PSII）含有两个辅助叶绿素（ChlZ，连接到D1-His 118，ChlD，连接到D2-His 117）、类胡萝卜素（Car）和血红素（cytochromeb 559）辅因子，它们在从O2-evolving complex到P680+的主要电子供体途径被抑制的条件下充当替代电子供体。在6至120 K的低温范围内，集胞藻PSII核心复合物和菠菜PSII膜中的氧化还原活性辅助叶绿素和Car的光氧化已通过近红外（近红外）吸光度、移位激发拉曼差谱（SERDS）和电子顺磁共振（EPR）光谱进行了表征。（1）在SynechocystisPSII核心复合物中仅在814 nm处观察到一个Chl+近红外带，基于先前对D1-H118 Q和D2-H117 Q突变体的光谱研究，将其归属于ChlZ+[Stewart，D. H、Cua，A.，奇泽姆，D.一、晚餐，B。一、Bocian，D. F.、和Brudvig，G. W.（1998）Biochemistry 37，10040 - 10046];（2）在菠菜PSII膜中在817和850 nm处观察到两个Chl+近红外带，其根据光照温度以可变的相对产率形成，并分别归属于ChlZ+和ChlD+;（3）Chl和Car阳离子自由基在低温下的稳定性存在显著差异，Car+的衰减速度更快;（4）在集胞藻PSII核心复合物中，Car+通过与QA-的重组而不是通过ChlZ/ChlD氧化而衰变，具有多相动力学，这归因于当蛋白质被冷冻时被捕获的蛋白质构象体的集合;（5）在菠菜PSII膜中，Car+主要通过与QA-复合而衰变，但也有部分通过形成850 nm的Chl阳离子自由基而衰变。ChlZ+在低温下的更大稳定性使我们能够确认先前分配给ChlZ+的共振拉曼带被正确分配。此外，这些阳离子的形成和衰变提供了深入了解替代电子捐赠途径P680+。
Photosystem II (PSII) contains two accessory chlorophylls (ChlZ, ligated to D1-His118, and ChlD, ligated to D2-His117), carotenoid (Car), and heme (cytochromeb559) cofactors that function as alternate electron donors under conditions in which the primary electron-donation pathway from the O2-evolving complex to P680+is inhibited. The photooxidation of the redox-active accessory chlorophylls and Car has been characterized by near-infrared (near-IR) absorbance, shifted-excitation Raman difference spectroscopy (SERDS), and electron paramagnetic resonance (EPR) spectroscopy over a range of cryogenic temperatures from 6 to 120 K in bothSynechocystisPSII core complexes and spinach PSII membranes. The following key observations were made: (1) only one Chl+near-IR band is observed at 814 nm inSynechocystisPSII core complexes, which is assigned to ChlZ+based on previous spectroscopic studies of the D1-H118Q and D2-H117Q mutants [Stewart, D. H., Cua, A., Chisholm, D. A., Diner, B. A., Bocian, D. F., and Brudvig, G. W. (1998)Biochemistry 37, 10040−10046]; (2) two Chl+near-IR bands are observed at 817 and 850 nm in spinach PSII membranes which are formed with variable relative yields depending on the illumination temperature and are assigned to ChlZ+, and ChlD+, respectively; (3) the Chl and Car cation radicals have significantly different stabilities at reduced temperatures with Car+decaying much faster; (4) inSynechocystisPSII core complexes, Car+decays by recombination with QA-and not by ChlZ/ChlDoxidation, with multiphasic kinetics that are attributed to an ensemble of protein conformers that are trapped as the protein is frozen; and (5) in spinach PSII membranes, Car+decays mainly by recombination with QA-, but also partly by formation of the 850 nm Chl cation radical. The greater stability of ChlZ+at low temperatures enabled us to confirm that resonance Raman bands previously assigned to ChlZ+are correctly assigned. In addition, the formation and decay of these cations provide insight into the alternate electron-donation pathways to P680+.