A rising tide of blue-absorbing biliprotein photoreceptors - characterization of seven such bilin-binding GAF domains in Nostoc sp PCC7120
A rising tide of blue-absorbing biliprotein photoreceptors - characterization of seven such bilin-binding GAF domains in Nostoc sp PCC7120
复制标题
蓝色吸收胆蛋白光感受器的兴起——发菜 PCC7120 中七个此类胆蛋白结合 GAF 结构域的表征
DOI：
10.1111/febs.12003
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发表时间：
2012-11-01
期刊：
影响因子：
5.4
通讯作者：
Zhou, Ming
中科院分区：
文献类型：
--
作者：
Ma, Qiong;Hua, Huan-Huan;Zhou, Ming
蓝细菌色素是蓝细菌中的光致变色感觉光感受器，其与光敏色素相关，但覆盖更宽的光谱范围。使用同源性搜索，一组推定的蓝色吸收光感受器被确定在念珠藻属PCC 7120，除了典型的发色团结合半胱氨酸的蓝藻色素，有一个保守的额外的半胱氨酸在DXCF基序。为了评估它们的光化学活性，假定的发色团结合GAF结构域在大肠杆菌中表达的藻蓝胆素生物合成的基因。除了一个共价结合的发色团，并表现出光可逆的光致变色反应，在约420 nm处的吸收在黑暗中形成的15 Z状态，和各种红移的吸收峰在490 - 600 nm范围内的光激活后形成的15 E状态。在变性条件下，共价结合的发色团被鉴定为藻蓝胆素、藻紫胆素或两者的混合物。典型的半胱氨酸和DXCF基序的半胱氨酸单独或一起突变。典型的半胱氨酸负责胆色素与脱辅基蛋白在C31处的稳定共价连接。DXCF基序中的半胱氨酸的第二个连接，可能是C10的发色团，产生蓝色吸收的红宝石型15 Z发色团，但在大多数情况下，在光转化为发色团的15 E异构体时，以及当用酸性尿素变性时，会丢失。
Cyanobacteriochromes are photochromic sensory photoreceptors in cyanobacteria that are related to phytochromes but cover a much broader spectral range. Using a homology search, a group of putative blue-absorbing photoreceptors was identified in Nostoc sp. PCC 7120 that, in addition to the canonical chromophore-binding cysteine of cyanobacteriochromes, have a conserved extra cysteine in a DXCF motif. To assess their photochemical activities, putative chromophore-binding GAF domains were expressed in Escherichia coli together with the genes for phycocyanobilin biosynthesis. All except one covalently bound a chromophore and showed photoreversible photochromic responses, with absorption at approximately 420 nm for the 15Z states formed in the dark, and a variety of red-shifted absorption peaks in the 490600 nm range for the 15E states formed after light activation. Under denaturing conditions, the covalently bound chromophores were identified as phycocyanobilin, phycoviolobilin or mixtures of both. The canonical cysteines and those of the DXCF motifs were mutated, singly or together. The canonical cysteine is responsible for stable covalent attachment of the bilin to the apo-protein at C31. The second linkage from the cysteine in the DXCF motif, probably to C10 of the chromophore, yields blue-absorbing rubin-type 15Z chromophores, but is lost in most cases upon photoconversion to the 15E isomers of the chromophores, and also when denatured with acidic urea.