Dipartimento di Chimica e Chimica Industriale, Universitá di Pisa, Via G. Moruzzi 13, 56124 Pisa, Italy.
J Phys Chem A. 2023 Jun 15;127(23):5065-5074. doi: 10.1021/acs.jpca.3c02385. Epub 2023 Jun 6.
We apply an integrated approach combining microsecond MD simulations and (polarizable) QM/MM calculations of NMR, FTIR, and UV-vis spectra to validate the structure of the light-activated form of the AppA photoreceptor, an example of blue light using flavin (BLUF) protein domain. The latter photoactivate through a proton-coupled electron transfer (PCET) that results in a tautomerization of a conserved glutamine residue in the active site, but this mechanism has never been spectroscopically proven for AppA, which has been always considered as an exception. Our simulations instead confirm that the spectral features observed upon AppA photoactivation are indeed directly connected to the tautomer form of glutamine as predicted by the PCET mechanism. In addition, we observe small but significant changes in the AppA structure, which are transmitted from the flavin binding pocket to the surface of the protein.
我们采用一种综合方法，结合微秒 MD 模拟和（极化）QM/MM 计算，对 NMR、FTIR 和 UV-vis 光谱进行计算，以验证 AppA 光感受器的光激活形式的结构，这是一种利用黄素（BLUF）蛋白结构域的蓝光（BLUF）蛋白结构域。后者通过质子耦合电子转移（PCET）进行光激活，导致活性位点中保守谷氨酰胺残基的互变异构，但该机制从未在 AppA 的光谱中得到证明，AppA 一直被认为是一个例外。相反，我们的模拟证实，在 AppA 光激活时观察到的光谱特征确实与 PCET 机制预测的谷氨酰胺互变异构形式直接相关。此外，我们观察到 AppA 结构的微小但显著的变化，这些变化从黄素结合口袋传递到蛋白质表面。
