Crystal structure of plant light-harvesting complex shows the active, energy-transmitting state
Crystal structure of plant light-harvesting complex shows the active, energy-transmitting state
复制标题
DOI：
10.1038/emboj.2008.276
复制
发表时间：
2009-02-04
期刊：
影响因子：
11.4
通讯作者：
Kuhlbrandt, Werner
中科院分区：
文献类型：
--
作者：
Barros, Tiago;Royant, Antoine;Kuhlbrandt, Werner
植物通过非光化学猝灭（NPQ）将多余的激发能以热量的形式消散。 NPQ 被认为类似于主要天线复合体、光系统 II (LHC-II) 的光捕获复合体的体外聚集猝灭。人们普遍认为这两个过程都涉及构象变化，从而在复合物中产生两个相邻颜料的猝灭中心。使用缺乏与猝灭相关的色素的重组 LHC-II，我们表明它们没有特殊的作用。 LHC-II 的单晶发出强烈的方向依赖性荧光，最大发射波长为 680 nm。主 680 nm 晶体发射在 100 K 下的平均寿命为 1.31 ns，但在相同条件下 LHC-II 聚集体的平均寿命仅为 0.39 ns。 LHC-II 单晶体的强发射和相对较长的荧光寿命表明该复合物未猝灭，因此晶体结构显示了 LHC-II 的活性、能量传输状态。我们得出的结论是，光捕获天线中激发能量的猝灭是由于与体外外部色素或体内其他色素-蛋白质复合物（例如 PsbS）的分子相互作用，并且不需要复合物内的构象变化。
Plants dissipate excess excitation energy as heat by non-photochemical quenching (NPQ). NPQ has been thought to resemble in vitro aggregation quenching of the major antenna complex, light harvesting complex of photosystem II (LHC-II). Both processes are widely believed to involve a conformational change that creates a quenching centre of two neighbouring pigments within the complex. Using recombinant LHC-II lacking the pigments implicated in quenching, we show that they have no particular role. Single crystals of LHC-II emit strong, orientation-dependent fluorescence with an emission maximum at 680 nm. The average lifetime of the main 680 nm crystal emission at 100 K is 1.31 ns, but only 0.39 ns for LHC-II aggregates under identical conditions. The strong emission and comparatively long fluorescence lifetimes of single LHC-II crystals indicate that the complex is unquenched, and that therefore the crystal structure shows the active, energy-transmitting state of LHC-II. We conclude that quenching of excitation energy in the light-harvesting antenna is due to the molecular interaction with external pigments in vitro or other pigment-protein complexes such as PsbS in vivo, and does not require a conformational change within the complex.