A Photo-Labile Thioether Linkage to Phycoviolobilin Provides the Foundation for the Blue/Green Photocycles in DXCF-Cyanobacteriochromes
A Photo-Labile Thioether Linkage to Phycoviolobilin Provides the Foundation for the Blue/Green Photocycles in DXCF-Cyanobacteriochromes
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DOI：
10.1016/j.str.2012.11.001
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发表时间：
2013-01-08
期刊：
影响因子：
5.7
通讯作者：
Vierstra, Richard D.
中科院分区：
文献类型：
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作者：
Burgie, E. Sethe;Walker, Joseph M.;Vierstra, Richard D.
光敏色素超家族包括植物和微生物中的光致变色光感受器的多样性集合，其采用在cGMP-磷酸二酯酶/腺苷酸环化酶/FhlA（GAF）结构域中的共价连接的胆色素来检测光。虽然大多数在红光和远红光吸收状态之间相互转换，但蓝细菌也表达称为蓝细菌色素（CBCR）的变体，其修改胆色素吸收以共同感知整个可见光谱。在这里，我们提出了两个X-射线晶体结构的GAF域的蓝色/绿色光致变色CBCR PixJ从细长热聚球藻。这些结构证实了CBCR通过异构化和第二硫醚键间接操纵发色团π-缀合系统的假设，在这种情况下，涉及蓝/绿色CBCR特征性的DXCF序列内的胆色素C10碳和Cys 494。生物化学研究支持一种光转换机制，即第二个链接在通往绿光吸收状态的途中断裂。总的来说，TePixJ（GAF）模型说明了光敏色素和CBCR在驾驶光感知方面的显着结构和光化学多功能性。
The phytochrome superfamily encompasses a diverse collection of photochromic photoreceptors in plants and microorganisms that employ a covalently linked bilin cradled in a cGMP-phosphodiesterase/adenylyl-cyclase/FhlA (GAF) domain to detect light. Whereas most interconvert between red- and far-red-light-absorbing states, cyanobacteria also express variants called cyanobacteriochromes (CBCRs) that modify bilin absorption to collectively perceive the entire visible spectrum. Here, we present two X-ray crystallographic structures of the GAF domain from the blue/green photochromic CBCR PixJ from Thermosynechococcus elongatus. These structures confirm the hypothesis that CBCRs variably manipulate the chromophore pi-conjugation system through isomerization and a second thioether linkage, in this case involving the bilin Cl 0 carbon and Cys494 within a DXCF sequence characteristic of blue/green CBCRs. Biochemical studies support a mechanism for photoconversion whereby the second linkage ruptures on route to the green-light-absorbing state. Collectively, the TePixJ(GAF) models illustrate the remarkable structural and photochemical versatility among phytochromes and CBCRs in driving light perception.