Commissariat à l'Energie Atomique, Institut de Biologie et Technologies de Saclay, 91191 Gif sur Yvette, France.
Proc Natl Acad Sci U S A. 2010 Jun 22;107(25):11620-5. doi: 10.1073/pnas.1002912107. Epub 2010 Jun 7.
High light can be lethal for photosynthetic organisms. Similar to plants, most cyanobacteria protect themselves from high irradiance by increasing thermal dissipation of excess absorbed energy. The photoactive soluble orange carotenoid protein (OCP) is essential for the triggering of this photoprotective mechanism. Light induces structural changes in the carotenoid and the protein, leading to the formation of a red active form. Through targeted gene interruption we have now identified a protein that mediates the recovery of the full antenna capacity when irradiance decreases. In Synechocystis PCC 6803, this protein, which we called the fluorescence recovery protein (FRP), is encoded by the slr1964 gene. Homologues of this gene are present in all of the OCP-containing strains. The FRP is a 14-kDa protein, strongly attached to the membrane, which interacts with the active red form of the OCP. In vitro this interaction greatly accelerates the conversion of the red OCP form to the orange form. We propose that in vivo, FRP plays a key role in removing the red OCP from the phycobilisome and in the conversion of the free red OCP to the orange inactive form. The discovery of FRP and its characterization are essential elements in the understanding of the OCP-related photoprotective mechanism in cyanobacteria.
高光对光合生物可能是致命的。与植物类似，大多数蓝藻通过增加过量吸收能量的热耗散来保护自己免受高光的伤害。光活性可溶性橙色类胡萝卜素蛋白 (OCP) 对于触发这种光保护机制是必不可少的。光诱导类胡萝卜素和蛋白质的结构变化，导致形成红色的活性形式。通过靶向基因中断，我们现在已经确定了一种蛋白质，当辐照度降低时，它介导恢复全天线容量。在集胞藻 PCC 6803 中，这种我们称为荧光恢复蛋白 (FRP) 的蛋白质由 slr1964 基因编码。该基因的同源物存在于所有含有 OCP 的菌株中。FRP 是一种 14kDa 的蛋白质，强烈附着在膜上，与 OCP 的活性红色形式相互作用。在体外，这种相互作用大大加速了红色 OCP 形式向橙色形式的转化。我们提出，在体内，FRP 起着关键作用，将红色 OCP 从藻胆体中去除，并将游离的红色 OCP 转化为橙色非活性形式。FRP 的发现及其特性是理解蓝藻中 OCP 相关光保护机制的重要因素。
