Photophysical diversity of two novel cyanobacteriochromes with phycocyanobilin chromophores: photochemistry and dark reversion kinetics
Photophysical diversity of two novel cyanobacteriochromes with phycocyanobilin chromophores: photochemistry and dark reversion kinetics
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两种具有藻蓝蛋白发色团的新型蓝细菌色素的光物理多样性：光化学和暗回复动力学
DOI：
10.1111/j.1742-4658.2011.08397.x
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发表时间：
2012-01-01
期刊：
影响因子：
5.4
通讯作者：
Zhao, Kai-Hong
中科院分区：
文献类型：
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作者：
Chen, Yu;Zhang, Juan;Zhao, Kai-Hong
蓝细菌色素是蓝细菌中作为感觉光感受器的光敏色素同系物。我们比较了两种蓝细菌色素，RGS（由slr 1393编码）从集胞藻属PCC 6803和AphC（由all 2699编码）从念珠藻属PCC 7120。两者都含有三个GAF（cGMP磷酸二酯酶、腺苷酸环化酶和FhlA蛋白）结构域（GAF 1、GAF 2和GAF 3）。将相应的全长、截短和半胱氨酸点突变基因与发色团生物合成基因一起在大肠杆菌中表达。 通过紫外-可见吸收、荧光和圆二色谱以及质谱法分析所得色蛋白。RGS显示出红-绿光致变色（λmax = 650和535 nm），这归因于与GAF 3的Cys 528结合的单个藻蓝胆素发色团（PCB）的可逆15 Z/E异构化。 在三个GAF结构域中，仅GAF 3结合发色团，并且结合是自催化的。RGS在体外自磷酸化;该反应是光调节的：含有E-PCB的535 nm状态比含有Z-PCB的650 nm状态更活跃。 念珠藻的AphC可以在两个GAF结构域（即GAF 1和GAF 3）处发色团化。PCB-GAF 1是光致变色的，其中提出的15 E状态（λmax = 685 nm）缓慢地热恢复到热稳定的15 Z状态（λmax = 635 nm）。 PCB-GAF 3显示出一种新的红橙色光致变色;不稳定状态（假定的15 E，λmax = 595 nm）非常迅速地（τ = 20 s）恢复到热稳定的Z状态（λmax = 645 nm）。 因此，双发色团化的AphC的光化学是复杂的，自磷酸化也是如此：E-GAF 1/E-GAF 3显示出最高的自磷酸化活性速率，而E-GAF 1/Z-GAF 3具有中等活性，Z-GAF 1/Z-GAF 3是最不活跃的状态。
Cyanobacteriochromes are phytochrome homologues in cyanobacteria that act as sensory photoreceptors. We compare two cyanobacteriochromes, RGS (coded by slr1393) from Synechocystis sp. PCC 6803 and AphC (coded by all2699) from Nostoc sp. PCC 7120. Both contain three GAF (cGMP phosphodiesterase, adenylyl cyclase and FhlA protein) domains (GAF1, GAF2 and GAF3). The respective full‐length, truncated and cysteine point‐mutated genes were expressed in Escherichia coli together with genes for chromophore biosynthesis. The resulting chromoproteins were analyzed by UV‐visible absorption, fluorescence and circular dichroism spectroscopy as well as by mass spectrometry. RGS shows a red–green photochromism (λmax = 650 and 535 nm) that is assigned to the reversible 15Z/E isomerization of a single phycocyanobilin‐chromophore (PCB) binding to Cys528 of GAF3. Of the three GAF domains, only GAF3 binds a chromophore and the binding is autocatalytic. RGS autophosphorylates in vitro; this reaction is photoregulated: the 535 nm state containing E‐PCB was more active than the 650 nm state containing Z‐PCB. AphC from Nostoc could be chromophorylated at two GAF domains, namely GAF1 and GAF3. PCB‐GAF1 is photochromic, with the proposed 15E state (λmax = 685 nm) reverting slowly thermally to the thermostable 15Z state (λmax = 635 nm). PCB‐GAF3 showed a novel red–orange photochromism; the unstable state (putative 15E, λmax = 595 nm) reverts very rapidly (τ∼ 20 s) back to the thermostable Z state (λmax = 645 nm). The photochemistry of doubly chromophorylated AphC is accordingly complex, as is the autophosphorylation: E‐GAF1/E‐GAF3 shows the highest rate of autophosphorylation activity, while E‐GAF1/Z‐GAF3 has intermediate activity, and Z‐GAF1/Z‐GAF3 is the least active state.