Antenna switches partners in the shade A cloudy day or an overshadowing tree causes fluctuations in light that can throw off the balance of energy flow in plant photosystems I and II (PSI and PSII). Pan et al. solved structures of PSI bound to two light-harvesting complexes (LHCs). One LHC is permanently associated with PSI. The other LHC delivers light energy to PSII under optimal conditions but can switch to a PSI-associated state after phosphorylation by a kinase that senses the redox environment of the chloroplast. The movement of LHCs between the photosystems helps maintain even energy flux. Two chlorophyll-containing subunits are visible in the structure that connect the PSI core to each LHC. Science, this issue p. 1109 Antenna proteins rearrange to balance energy flow to photosystems in fluctuating-light environments. Plants regulate photosynthetic light harvesting to maintain balanced energy flux into photosystems I and II (PSI and PSII). Under light conditions favoring PSII excitation, the PSII antenna, light-harvesting complex II (LHCII), is phosphorylated and forms a supercomplex with PSI core and the PSI antenna, light-harvesting complex I (LHCI). Both LHCI and LHCII then transfer excitation energy to the PSI core. We report the structure of maize PSI-LHCI-LHCII solved by cryo–electron microscopy, revealing the recognition site between LHCII and PSI. The PSI subunits PsaN and PsaO are observed at the PSI-LHCI interface and the PSI-LHCII interface, respectively. Each subunit relays excitation to PSI core through a pair of chlorophyll molecules, thus revealing previously unseen paths for energy transfer between the antennas and the PSI core.

中文翻译：

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具有光捕获复合物 I 和 II 的玉米光系统 I 超复合物的结构

天线在阴凉处切换伙伴 阴天或阴暗的树木会导致光线波动，从而破坏植物光系统 I 和 II（PSI 和 PSII）中的能量流平衡。潘等人。解决的 PSI 结构与两个光捕获复合物 (LHC) 结合。一台 LHC 与 PSI 永久关联。另一个 LHC 在最佳条件下向 PSII 提供光能，但在被感知叶绿体氧化还原环境的激酶磷酸化后可以切换到 PSI 相关状态。LHC 在光系统之间的运动有助于保持均匀的能量通量。在将 PSI 核心连接到每个 LHC 的结构中，可以看到两个含叶绿素的亚基。科学，这个问题 p。1109 天线蛋白质重新排列以平衡光系统在波动光环境中的能量流。植物调节光合光收集以维持进入光系统 I 和 II（PSI 和 PSII）的平衡能量通量。在有利于 PSII 激发的光照条件下，PSII 天线、光捕获复合物 II (LHCII) 被磷酸化并与 PSI 核心和 PSI 天线、光捕获复合物 I (LHCI) 形成超级复合物。然后 LHCI 和 LHCII 都将激发能量转移到 PSI 核心。我们报告了通过冷冻电子显微镜解析的玉米 PSI-LHCI-LHCII 的结构，揭示了 LHCII 和 PSI 之间的识别位点。PSI 亚基 PsaN 和 PsaO 分别在 PSI-LHCI 界面和 PSI-LHCII 界面处观察到。每个亚基通过一对叶绿素分子将激发传递到 PSI 核心，从而揭示了以前看不见的天线和 PSI 核心之间能量转移的路径。