Structural Evidence of Photoisomerization Pathways in Fluorescent Proteins
Structural Evidence of Photoisomerization Pathways in Fluorescent Proteins
复制标题
DOI：
10.1021/jacs.9b08356
复制
发表时间：
2019-10-02
影响因子：
15
通讯作者：
Boxer, Steven G.
中科院分区：
文献类型：
--
作者：
Chang, Jeffrey;Romei, Matthew G.;Boxer, Steven G.
绿色荧光蛋白(GFP)生色团等分子中的双键光致异构化可以通过体积需求的单键翻转途径或通过体积守恒的呼啦扭转途径发生。了解决定光异构化途径的因素将有助于合理设计可光开关GFP作为改进的超分辨显微镜工具。在这篇通讯中，我们通过求解含有一氯化生色团的顺式和反式rsEGFP2的晶体结构，揭示了一种可光开关的绿色荧光蛋白rsEGFP2的光异构化途径。氯取代基在反式状态的位置破坏了发色团酚环的对称性，使我们能够区分这两条途径。令人惊讶的是，我们发现这一途径取决于蛋白质单体在晶格中的排列：在较松散的堆积中，发生单键翻转，而在较紧密的堆积(单位晶胞尺寸小7%)中，出现呼啦圈扭曲。
Double-bond photoisomerization in molecules such as the green fluorescent protein (GFP) chromophore can occur either via a volume-demanding one-bond-flip pathway or via a volume-conserving hula-twist pathway. Understanding the factors that determine the pathway of photoisomerization would inform the rational design of photoswitchable GFPs as improved tools for super-resolution microscopy. In this communication, we reveal the photoisomerization pathway of a photoswitchable GFP, rsEGFP2, by solving crystal structures of cis and trans rsEGFP2 containing a monochlorinated chromophore. The position of the chlorine substituent in the trans state breaks the symmetry of the phenolate ring of the chromophore and allows us to distinguish the two pathways. Surprisingly, we find that the pathway depends on the arrangement of protein monomers within the crystal lattice: in a looser packing, the one-bond-flip occurs, whereas, in a tighter packing (7% smaller unit cell size), the hula-twist occurs.