Spectroscopic analysis of the dark relaxation process of a photocycle in a sensor of blue light using FAD (BLUF) protein Slr1694 of the cyanobacterium Synechocystis sp PCC6803
Spectroscopic analysis of the dark relaxation process of a photocycle in a sensor of blue light using FAD (BLUF) protein Slr1694 of the cyanobacterium Synechocystis sp PCC6803
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DOI：
10.1093/pcp/pci003
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发表时间：
2005-01-01
影响因子：
4.9
通讯作者：
Ono, TA
中科院分区：
文献类型：
--
作者：
Hasegawa, K;Masuda, S;Ono, TA
Slr 1694是蓝细菌集胞藻PCC 6803中的一种BLUF（使用黄素腺嘌呤二核苷酸的蓝光传感器）蛋白和推定的光感受器。照明的Slr 1694诱导的信号光状态的同时，在紫外-可见吸收的黄素，和形成的带从黄素和脱辅基蛋白质的光减暗傅立叶变换红外（FTIR）差光谱的红移。用苯丙氨酸取代Tyr 8消除了这些变化。光态弛豫到基态暗态，在此期间FTIR谱带发生单相衰减。这些谱带根据它们的衰变速率可分为三组。黄素异咯嗪环的C4=O伸缩带衰减速率最高，与吸收红移相对应。结果表明，C4=O上的氢键是导致紫外-可见光红移的主要原因，与密度泛函计算结果一致.所有的FTIR谱带和红移在氘代的SLR 1694中以相同的较慢速率衰减。这些结果表明，暗弛豫从轻状态是有限的质子转移。相比之下，在脱水条件下形成的受约束的光状态衰变得更慢，没有氘代效应。提出了一种涉及质子转移的光循环机理。
Slr1694 is a BLUF (sensor of blue light using flavin adenine dinucleotide) protein and a putative photoreceptor in the cyanobacterium Synechocystis sp. PCC6803. Illumination of Slr1694 induced a signaling light state concurrent with a red shift in the UV-visible absorption of flavin, and formation of the bands from flavin and apo-protein in the light-minus-dark Fourier transform infrared (FTIR) difference spectrum. Replacement of Tyr8 with phenylalanine abolished these changes. The light state relaxed to the ground dark state, during which the FTIR bands decayed monophasically. These bands were classifiable into three groups according to their decay rates. The C4=O stretching bands of a flavin isoalloxazine ring had the highest decay rate, which corresponded to that of the absorption red shift. The result indicated that the hydrogen bonding at C4=O is responsible for the UV-visible red shift, consistent with the results of density functional calculation. All FTIR bands and the red shift decayed at the same slower rate in deuterated Slr1694. These results indicated that the dark relaxation from the light state is limited by proton transfer. In contrast, a constrained light state formed under dehydrated conditions decayed much more slowly with no deuteration effects. A photocycle mechanism involving the proton transfer was proposed.