PDF(Pubmed)
Abstract：
Cyanobacteria were the first microorganisms that released oxygen into the atmosphere billions of years ago. To do it safely under intense sunlight, they developed strategies that prevent photooxidation in the photosynthetic membrane, by regulating the light-harvesting activity of their antenna complexes-the phycobilisomes-via the orange-carotenoid protein (OCP). This water-soluble protein interacts with the phycobilisomes and triggers nonphotochemical quenching (NPQ), a mechanism that safely dissipates overexcitation in the membrane. To date, the mechanism of action of OCP in performing NPQ is unknown. In this work, we performed ultrafast spectroscopy on a minimal NPQ system composed of the active domain of OCP bound to the phycobilisome core. The use of this system allowed us to disentangle the signal of the carotenoid from that of the bilins. Our results demonstrate that the binding to the phycobilisomes modifies the structure of the ketocarotenoid associated with OCP. We show that this molecular switch activates NPQ, by enabling excitation-energy transfer from the antenna pigments to the ketocarotenoid.
摘要：
蓝细菌是数十亿年前释放氧气到大气中的第一种微生物。在强烈的阳光下安全地做这件事，他们开发了防止光合膜光氧化的策略，通过橙色类胡萝卜素蛋白（OCP）调节其天线复合物-藻胆体的光捕获活性。这种水溶性蛋白质与藻胆体相互作用并触发非光化学猝灭（NPQ），一种安全消散膜中过度兴奋的机制。迄今为止,OCP在执行NPQ中的作用机制未知。在这项工作中,我们在最小NPQ系统上进行了超快光谱，该系统由与藻胆体核心结合的OCP活性域组成。使用该系统使我们能够将类胡萝卜素的信号与胆红素的信号分开。我们的结果表明，与藻胆体的结合会改变与OCP相关的酮类结构。我们证明了这个分子开关激活了NPQ，通过使激发能量转移从天线颜料到酮类。
