High-resolution Mn EXAFS of the oxygen-evolving complex in photosystem II:: Structural implications for the Mn4Ca cluster
High-resolution Mn EXAFS of the oxygen-evolving complex in photosystem II:: Structural implications for the Mn4Ca cluster
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DOI：
10.1021/ja054873a
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发表时间：
2005-11-02
影响因子：
15
通讯作者：
Yachandra, V
中科院分区：
文献类型：
--
作者：
Yano, J;Pushkar, Y;Yachandra, V
光系统II(PS II)中的放氧复合体生物产氧是自然界最重要的反应之一。最近的X射线晶体结构，虽然受到3.2Mn3.5ra的分辨率的限制，但已经定位了与−簇相关的电子密度在多蛋白PS II复合体中。详细的结构关键取决于来自光谱技术的输入，如EXAFS和EPR/Endor，因为X射线衍射的分辨率不能准确确定Mn/Ca或桥联和末端配体原子的位置。由EXAFS确定的Mn-−、Mn/Ca/配体相互作用的数目和距离为Mn4Ca团簇的结构提供了重要的限制条件。在这里，我们提供了使用新型多晶单色仪的高分辨率EXAFS方法的数据，该方法显示了三个较短的Mn-−-Mn距离在2.7到2.8？之间，因此，在Mn4Ca团簇中存在三个二μ-氧桥联单元。这一结果对基于光谱和衍射数据的拟议结构施加了明显的限制，并为改进此类结构提供了输入。
The biological generation of oxygen by the oxygen-evolving complex in photosystem II (PS II) is one of nature's most important reactions. The recent X-ray crystal structures, while limited by resolutions of 3.2−3.5 Å, have located the electron density associated with the Mn4Ca cluster within the multiprotein PS II complex. Detailed structures critically depend on input from spectroscopic techniques, such as EXAFS and EPR/ENDOR, as the XRD resolution does not allow for accurate determination of the position of Mn/Ca or the bridging and terminal ligand atoms. The number and distances of Mn−Mn/Ca/ligand interactions determined from EXAFS provide important constraints for the structure of the Mn4Ca cluster. Here, we present data from a high-resolution EXAFS method using a novel multicrystal monochromator that show three short Mn−Mn distances between 2.7 and 2.8 Å and, hence, the presence of three di-μ-oxo-bridged units in the Mn4Ca cluster. This result imposes clear limitations on the proposed structures based on spectroscopic and diffraction data and provides input for refining such structures.