Fudim Roman, Mehlhorn Jennifer, Berthold Thomas, Weber Stefan, Schleicher Erik, Kennis John T M, Mathes Tilo
Institut für Biologie/Experimentelle Biophysik, Humboldt Universität zu Berlin, Berlin, Germany.
Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany.
FEBS J. 2015 Aug;282(16):3161-74. doi: 10.1111/febs.13297. Epub 2015 May 6.
Blue light receptors using FAD (BLUFs) facilitate blue light-induced signal transduction via light-induced rearrangement of hydrogen bonds between the flavin chromophore and a conserved glutamine side chain. Here, we investigated the photochemistry of the BLUF domain Slr1694 from Synechocystis sp. in which the glutamine side chain was removed. Without the glutamine, no red-shifted signaling state is formed, but light-induced proton-coupled electron transfer between protein and flavin takes place similarly as for the wild-type protein. However, the lifetime of the neutral flavin semiquinone-tyrosyl radical pair is greatly prolonged from < 100 ps to several nanoseconds, which indicates that the formation of radical intermediates drives the hydrogen bond rearrangement in BLUF photoactivation. Moreover, glutamine plays a central role in the molecular organization of the hydrogen bond network in the flavin-binding pocket, as its removal enhances electron transfer from tyrosine to the excited flavin, and enables competing electron transfer from a nearby tryptophan.
使用黄素腺嘌呤二核苷酸（FAD）的蓝光受体（BLUFs）通过黄素发色团与保守的谷氨酰胺侧链之间氢键的光诱导重排促进蓝光诱导的信号转导。在此，我们研究了来自集胞藻属（Synechocystis sp.）的BLUF结构域Slr1694的光化学性质，其中谷氨酰胺侧链已被去除。没有谷氨酰胺时，不会形成红移的信号状态，但蛋白质与黄素之间的光诱导质子耦合电子转移与野生型蛋白质类似地发生。然而，中性黄素半醌 - 酪氨酸自由基对的寿命从<100皮秒大大延长至几纳秒，这表明自由基中间体的形成驱动了BLUF光激活中的氢键重排。此外，谷氨酰胺在黄素结合口袋中氢键网络的分子组织中起核心作用，因为其去除增强了从酪氨酸到激发黄素的电子转移，并使来自附近色氨酸的竞争性电子转移成为可能。
