Spin-Density Distribution, Conformation, and Hydrogen Bonding of the Redox-Active Tyrosine YZ in Photosystem II from Multiple-Electron Magnetic-Resonance Spectroscopies: Implications for Photosynthetic Oxygen Evolution
Spin-Density Distribution, Conformation, and Hydrogen Bonding of the Redox-Active Tyrosine YZ in Photosystem II from Multiple-Electron Magnetic-Resonance Spectroscopies: Implications for Photosynthetic Oxygen Evolution
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多电子磁共振波谱光系统 II 中氧化还原活性酪氨酸 YZ 的自旋密度分布、构象和氢键：对光合放氧的影响
DOI：
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发表时间：
1995
期刊：
影响因子：
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通讯作者：
G. Babcock
中科院分区：
文献类型：
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作者：
C. Tommos;Xiao;K. Warncke;C. Hoganson;S. Styring;J. McCracken;B. Diner;G. Babcock
参与光合作用氧气放出的氧化还原活性 Y{sub Z} 酪氨酰残基的氧化形式已在集胞藻 6803 D2-Y160F 突变株的 Mn 耗尽光系统 II 核心复合物中生成并捕获。该系统消除了 P{sub 700}{sup +} 和 Y{sub D}D+{center_dot} 的干扰，并允许表征 Y{sub Z}{sup {center_dot}} 通过结合使用特定的 {sup 2}H 标记和电子磁共振技术，包括 CW-EPR、调频和瞬态检测 ENDOR 以及 {sup 2}H-ESEEM。利用这些互补技术，我们对 Y{sub Z}{sup {center_dot}} 的超精细结构进行了详细评估，并获得了与弱耦合核的偶极相互作用、环氢的强各向异性张量以及与 {Beta}-亚甲基位点的各向同性相互作用。我们得出的结论是，酪氨酰自由基并没有通过氢键效应大规模调节其自旋密度来调节特定的功能。我们建议水氧化中 Y{sub Z} 的氢原子转移函数。在此模型中，(Mn){sub 4}/Y{sub Z} 中心形成光系统 II 的析氧复合物，其中 (Mn){sub 4} 簇结合底物水并使氧化当量离域，而 Y{sub Z} 通过以协调或顺序的方式从底物水中提取氢来发挥作用。 71 条参考文献，8 个图，更多 » 2 个标签。« 更少
The oxidized form of the redox-active Y{sub Z} tyrosyl residue involved in photosynthetic oxygen evolution has been generated and trapped in Mn-depleted Photosystem II core complexes from a D2-Y160F mutant strain of Synechocystis 6803. This system eliminates interference from P{sub 700}{sup +} and Y{sub D}D+{center_dot} and allowed characterization of Y{sub Z}{sup {center_dot}} by using a combination of specific {sup 2}H-labeling and electron magnetic-resonance techniques that included CW-EPR, frequency-modulated and transient detected ENDOR, and {sup 2}H-ESEEM. Using these complementary techniques, we have carried out a detailed evaluation of the hyperfine structure of Y{sub Z}{sup {center_dot}} and obtained the dipolar interactions to weakly coupled nuclei, the strongly anisotropic tensors of the ring-hydrogens, and the more isotropic interactions to the {Beta}-methylene site. We conclude that tyrosyl radicals are not tuned to specific function by large-scale modulations of their spin density through hydrogen-bonding effects. We suggest a hydrogen-atom transfer function for Y{sub Z} in water oxidation. Within this model, the (Mn){sub 4}/Y{sub Z} center forms the Oxygen-Evolving Complex of Photosystem II where the (Mn){sub 4} cluster binds substrate water and delocalizes oxidizing equivalents and Y{sub Z} acts by abstracting hydrogens from substrate water in either a concerted or sequential fashion. 71 refs., 8 figs.,more » 2 tabs.« less