Schmidt Marius, Patel Anamika, Zhao Yi, Reuter Wolfgang
Physikdepartment E17, Technische Universität München, James Franck Strasse, 85747 Garching, Germany.
Biochemistry. 2007 Jan 16;46(2):416-23. doi: 10.1021/bi061844j.
Phycobiliproteins and phytochromes are light-harvesting and light-sensing proteins containing linear tetrapyrroles, so-called bile chromophores. The chromophores in certain biliproteins, including the phytochromes, isomerize reversibly from a stable Z-configuration to a stable E-configuration when irradiated with light of the appropriate wavelength. Here, we report the crystal structure of alpha-phycoerythrocyanin with its chromophore in the E-configuration, compare it with the Z-configuration found in trimeric phycoerythrocyanin, and reveal the structural bases of the isomerization. The geometric changes of the chromophore account for the large spectral shift, which characterizes the overall transition. Interactions of the chromophore A and D pyrrole rings with flexible protein moieties are required for the formation and stabilization of the isomers. We predict that the results will hold for all photoactive biliproteins.
藻胆蛋白和植物色素是含有线性四吡咯（即所谓的胆汁发色团）的光捕获和光感应蛋白。某些胆蛋白（包括植物色素）中的发色团在受到适当波长的光照射时，会从稳定的Z构型可逆地异构化为稳定的E构型。在此，我们报道了α-藻红蛋白与其发色团处于E构型时的晶体结构，将其与三聚体藻红蛋白中发现的Z构型进行比较，并揭示异构化的结构基础。发色团的几何变化解释了作为整体转变特征的大光谱位移。发色团A和D吡咯环与柔性蛋白质部分的相互作用是异构体形成和稳定所必需的。我们预测这些结果适用于所有光活性胆蛋白。
