Zirak P, Penzkofer A, Lehmpfuhl C, Mathes T, Hegemann P
Institut II - Experimentelle und Angewandte Physik, Universität Regensburg, Universitätstrasse 31, D-93053 Regensburg, Germany.
J Photochem Photobiol B. 2007 Jan 3;86(1):22-34. doi: 10.1016/j.jphotobiol.2006.08.007. Epub 2006 Sep 22.
The BLUF protein Slr1694 from the cyanobacterium Synechocystis sp. PCC6803 is characterized by absorption and emission spectroscopy. Slr1694 expressed from E. coli which non-covalently binds FAD, FMN, and riboflavin (called Slr1694(I)), and reconstituted Slr1694 which dominantly contains FAD (called Slr1694(II)) are investigated. The receptor conformation of Slr1694 (dark adapted form Slr1694(r)) is transformed to the putative signalling state (light adapted form Slr1694(s)) with red-shifted absorption and decreased fluorescence efficiency by blue-light excitation. In the dark at 22 degrees C, the signalling state recovers back to the initial receptor state with a time constants of about 14.2s for Slr1694(I) and 17s for Slr1694(II). Quantum yields of signalling state formation of approximately 0.63+/-0.07 for both Slr1694(I) and Slr1694(II) were determined by transient transmission measurements and intensity dependent steady-state transmission measurements. Extended blue-light excitation causes some bound flavin conversion to the hydroquinone form and some photo-degradation, both with low quantum efficiency. The flavin-hydroquinone re-oxidizes slowly back (time constant 5-9 min) to the initial flavoquinone form in the dark. A photo-cycle dynamics scheme is presented.
来自集胞藻属蓝藻 Synechocystis sp. PCC6803 的 BLUF 蛋白 Slr1694 通过吸收光谱和发射光谱进行表征。对从大肠杆菌表达的非共价结合 FAD、FMN 和核黄素的 Slr1694（称为 Slr1694(I)）以及主要含有 FAD 的重组 Slr1694（称为 Slr1694(II)）进行了研究。通过蓝光激发，Slr1694 的受体构象（暗适应形式 Slr1694(r)）转变为假定的信号状态（光适应形式 Slr1694(s)），吸收峰红移且荧光效率降低。在 22 摄氏度的黑暗环境中，信号状态恢复到初始受体状态，Slr1694(I) 的时间常数约为 14.2 秒，Slr1694(II) 的时间常数约为 17 秒。通过瞬态透射测量和强度依赖稳态透射测量确定，Slr1694(I) 和 Slr1694(II) 的信号状态形成的量子产率约为 0.63±0.07。延长蓝光激发会导致一些结合的黄素转化为对苯二酚形式并发生一些光降解，两者的量子效率都很低。黄素 - 对苯二酚在黑暗中会缓慢地重新氧化（时间常数为 5 - 9 分钟）回到初始的黄素醌形式。本文提出了一个光循环动力学方案。
