Trunk Florian, Köhler Lisa, Fischer Tobias, Gärtner Wolfgang, Song Chen, Slavov Chavdar, Wachtveitl Josef
Institute of Physical and Theoretical Chemistry, Goethe University Frankfurt am Main, Max-von-Laue-Straße 7, 60438, Frankfurt, Germany.
Institute for Analytical Chemistry, University of Leipzig, Linnéstraße 3, 04103, Leipzig, Germany.
Chemphyschem. 2025 Mar 15;26(6):e202401022. doi: 10.1002/cphc.202401022. Epub 2025 Jan 15.
The light-sensing activity of phytochromes is based on the reversible light-induced switching between two isomerization states of the bilin chromophore. These photo-transformations may not necessarily be only unidirectional, but could potentially branch back to the initial ground state in a thermally driven process termed shunt. Such shunts have been rarely reported, and thus our understanding of this process and its governing factors are limited. Here, we aim to close this gap by providing coherent experimental evidence of a shunt process using UV/Vis laser flash photolysis. We studied the Pfr to Pr dynamics of the single GAF domain (g1) construct of the knotless phytochrome All2699 from cyanobacterium Nostoc punctiforme. We identified a shunt that can be switched on and off by ambient buffer conditions. In combination with H/D exchange and kinetic modeling, we propose a keto-enol tautomerism to allow for the thermal isomerization of the chromophore and act as the driver of the shunt transition.
光敏色素的光感应活性基于胆色素发色团两种异构化状态之间可逆的光诱导转换。这些光转化不一定只是单向的，而是有可能在一个称为“分流”的热驱动过程中回到初始基态。这种分流很少被报道，因此我们对这一过程及其控制因素的理解有限。在这里，我们旨在通过使用紫外/可见激光闪光光解提供分流过程的连贯实验证据来填补这一空白。我们研究了来自点状念珠藻的无结光敏色素All2699的单个GAF结构域（g1）构建体从Pfr到Pr的动力学。我们发现了一种可以通过环境缓冲条件打开和关闭的分流。结合氢/氘交换和动力学建模，我们提出了一种酮-烯醇互变异构，以实现发色团的热异构化，并作为分流转变的驱动因素。
