Evidence for an early green/red photocycle that precedes the diversification of GAF domain photoreceptor cyanobacteriochromes
Evidence for an early green/red photocycle that precedes the diversification of GAF domain photoreceptor cyanobacteriochromes
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DOI：
10.1007/s43630-023-00387-4
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发表时间：
2023-02
影响因子：
3.1
通讯作者：
Nibedita Priyadarshini;Niklas Steube;Dennis Wiens;R. Narikawa;A. Wilde;Georg K. A. Hochberg;Gen Enomoto
中科院分区：
文献类型：
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作者：
Nibedita Priyadarshini;Niklas Steube;Dennis Wiens;R. Narikawa;A. Wilde;Georg K. A. Hochberg;Gen Enomoto
光敏色素是真核生物和细菌中的线性四吡咯结合光受体，主要可逆地响应红光和远红光信号。在基于GAF结构域的光敏色素超家族中，蓝藻特异性的蓝藻色素显示覆盖整个可见光区域的各种光学性质。目前尚不清楚是什么生理需求推动了蓝细菌中蓝细菌色素的进化。在这里，我们利用祖先序列重建和生化验证，显示复活的祖先蓝藻色素蛋白可逆地响应绿色和红色光信号。pH滴定分析表明，结合的藻蓝胆素发色团的去质子化是至关重要的感知绿色光。祖先的蓝藻色素显示只有适度的热逆转的绿色光吸收形式，这表明他们进化到感测入射的绿色/红色光的比例。许多蓝藻可以利用藻胆体捕光复合物利用绿色光进行光合作用。绿色/红色传感蓝细菌色素可能通过色适应来重新排列藻胆体的吸收能力，从而更好地适应不断变化的光环境。
Phytochromes are linear tetrapyrrole-binding photoreceptors in eukaryotes and bacteria, primarily responding to red and far-red light signals reversibly. Among the GAF domain-based phytochrome superfamily, cyanobacteria-specific cyanobacteriochromes show various optical properties covering the entire visible region. It is unknown what physiological demands drove the evolution of cyanobacteriochromes in cyanobacteria. Here, we utilize ancestral sequence reconstruction and biochemical verification to show that the resurrected ancestral cyanobacteriochrome proteins reversibly respond to green and red light signals. pH titration analyses indicate that the deprotonation of the bound phycocyanobilin chromophore is crucial to perceive green light. The ancestral cyanobacteriochromes show only modest thermal reversion to the green light-absorbing form, suggesting that they evolved to sense the incident green/red light ratio. Many cyanobacteria can utilize green light for photosynthesis using phycobilisome light-harvesting complexes. The green/red sensing cyanobacteriochromes may have allowed better acclimation to changing light environments by rearranging the absorption capacity of the phycobilisome through chromatic acclimation.Graphical abstract