Huber Christina, Strack Merle, Schultheiß Isabel, Pielage Julia, Mechler Xenia, Hornbogen Justin, Diller Rolf, Frankenberg-Dinkel Nicole
Department of Microbiology, Rheinland-Pfälzische Technische Universität Kaiserslautern-Landau, Kaiserslautern, Germany.
Department of Physics, Rheinland-Pfälzische Technische Universität Kaiserslautern-Landau, Kaiserslautern, Germany.
J Biol Chem. 2024 Apr;300(4):107148. doi: 10.1016/j.jbc.2024.107148. Epub 2024 Mar 9.
Bathy phytochromes are a subclass of bacterial biliprotein photoreceptors that carry a biliverdin IXα chromophore. In contrast to prototypical phytochromes that adopt a red-light-absorbing Pr ground state, the far-red light-absorbing Pfr-form is the thermally stable ground state of bathy phytochromes. Although the photobiology of bacterial phytochromes has been extensively studied since their discovery in the late 1990s, our understanding of the signal transduction process to the connected transmitter domains, which are often histidine kinases, remains insufficient. Initiated by the analysis of the bathy phytochrome PaBphP from Pseudomonas aeruginosa, we performed a systematic analysis of five different bathy phytochromes with the aim to derive a general statement on the correlation of photostate and autokinase output. While all proteins adopt different Pr/Pfr-fractions in response to red, blue, and far-red light, only darkness leads to a pure or highly enriched Pfr-form, directly correlated with the lowest level of autokinase activity. Using this information, we developed a method to quantitatively correlate the autokinase activity of phytochrome samples with well-defined stationary Pr/Pfr-fractions. We demonstrate that the off-state of the phytochromes is the Pfr-form and that different Pr/Pfr-fractions enable the organisms to fine-tune their kinase output in response to a certain light environment. Furthermore, the output response is regulated by the rate of dark reversion, which differs significantly from 5 s to 50 min half-life. Overall, our study indicates that bathy phytochromes function as sensors of light and darkness, rather than red and far-red light, as originally postulated.
深海藻胆蛋白是一类细菌双蛋白光感受器的亚类，其携带一个藻胆素IXα发色团。与采用吸收红光的Pr基态的典型藻胆蛋白不同，吸收远红光的Pfr形式是深海藻胆蛋白的热稳定基态。尽管自20世纪90年代末发现细菌藻胆蛋白以来，对其光生物学进行了广泛研究，但我们对与通常为组氨酸激酶的相连信号转导结构域的信号转导过程的理解仍然不足。以对铜绿假单胞菌的深海藻胆蛋白PaBphP的分析为开端，我们对五种不同的深海藻胆蛋白进行了系统分析，目的是得出关于光态与自身激酶输出相关性的一般性结论。虽然所有蛋白质在响应红光、蓝光和远红光时采用不同的Pr/Pfr比例，但只有黑暗会导致纯的或高度富集的Pfr形式，这与最低水平的自身激酶活性直接相关。利用这些信息，我们开发了一种方法，将藻胆蛋白样品的自身激酶活性与明确的稳定Pr/Pfr比例进行定量关联。我们证明藻胆蛋白的关闭状态是Pfr形式，并且不同的Pr/Pfr比例使生物体能够根据特定的光环境微调其激酶输出。此外，输出响应受暗逆转速率的调节，暗逆转半衰期从5秒到50分钟有显著差异。总体而言，我们的研究表明，深海藻胆蛋白作为光和黑暗的传感器发挥作用，而不是像最初假设的那样作为红光和远红光的传感器。
