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Nature:“光系统II”的X-射线结构

摘要 : 发表于2014年7月9日的《Natrue》杂志上的一篇论文中,收集到了关于光合作用的“光系统II”的小晶体在其从“暗”的S1状态向双激发的S3状态转变过程中的具有时间分辨率的SFX数据。

Nature:“光系统II”的X-射线结构

人们最近发现,来自X-射线自由电子激光器的极短和极强的辐射脉冲,可被用来在纳米至微米大小的蛋白晶体受到辐射损害之前获得它们的衍射数据。人们希望,这种“序列飞秒晶体学”(SFX)方法将能够获得那些不会产生非常有序的宏观晶体的蛋白和蛋白复合物的结构。

本文作者收集到了关于光合作用的“光系统II”的小晶体在其从“暗”的S1状态向双激发的S3状态转变过程中的具有时间分辨率的SFX数据。当前,这一方法的分辨率还不是很高,但却足以显示位于“放氧复合体”核心的Mn4CaO5团簇上以及电子受体点上发生的显著的构形变化。

原文摘要:

Serial time-resolved crystallography of photosystem II using a femtosecond X-ray laser

Christopher Kupitz, Shibom Basu, Ingo Grotjohann, Raimund Fromme, Nadia A. Zatsepin,Kimberly N. Rendek, Mark S. Hunter, Robert L. Shoeman, Thomas A. White, Dingjie Wang,Daniel James, Jay-How Yang, Danielle E. Cobb, Brenda Reeder, Raymond G. Sierra,Haiguang Liu, Anton Barty, Andrew L. Aquila, Daniel Deponte, Richard A. Kirian, Sadia Bari,Jesse J. Bergkamp, Kenneth R. Beyerlein, Michael J. Bogan, Carl Caleman et al.

Photosynthesis, a process catalysed by plants, algae and cyanobacteria converts sunlight to energy thus sustaining all higher life on Earth. Two large membrane protein complexes, photosystem I and II (PSI and PSII), act in series to catalyse the light-driven reactions in photosynthesis. PSII catalyses the light-driven water splitting process, which maintains the Earth’s oxygenic atmosphere. In this process, the oxygen-evolving complex (OEC) of PSII cycles through five states, S0 to S4, in which four electrons are sequentially extracted from the OEC in four light-driven charge-separation events. Here we describe time resolved experiments on PSII nano/microcrystals from Thermosynechococcus elongatus performed with the recently developed technique of serial femtosecond crystallography. Structures have been determined from PSII in the dark S1 state and after double laser excitation (putative S3 state) at 5 and 5.5 Å resolution, respectively. The results provide evidence that PSII undergoes significant conformational changes at the electron acceptor side and at the Mn4CaO5 core of the OEC. These include an elongation of the metal cluster, accompanied by changes in the protein environment, which could allow for binding of the second substrate water molecule between the more distant protruding Mn (referred to as the ‘dangler’ Mn) and the Mn3CaOx cubane in the S2 to S3 transition, as predicted by spectroscopic and computational studies. This work shows the great potential for time-resolved serial femtosecond crystallography for investigation of catalytic processes in biomolecules.

对应Nature杂志: 2014年9月11日Nature杂志精选

来源: Nature 浏览次数:131

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