Chemistry Department, Connecticut College, New London, CT 06320, USA.
J Phys Chem B. 2010 Nov 25;114(46):15362-9. doi: 10.1021/jp107119q. Epub 2010 Nov 3.
Tsien et al. (Science, 2009, 324, 804-807) recently reported the creation of the first infrared fluorescent protein (IFP). It was engineered from bacterial phytochrome by removing the PHY and histidine kinase-related domains, by optimizing the protein to prevent dimerization, and by limiting the biliverdins conformational freedom, especially around its D ring. We have used database analyses and molecular dynamics simulations with freely rotating chromophoric dihedrals in order to model the dihedral freedom available to the biliverdin D ring in the excited state and to show that the tetrapyrrole ligands in phytochromes are flexible and can adopt many conformations; however, their conformational space is limited/defined by the chemospatial characteristics of the protein cavity. Our simulations confirm that the reduced accessibility to conformations geared to an excited state proton transfer may be responsible for the fluorescence in IFP, just as has been suggested by Kennis et al. (Proc. Natl. Acad. Sci. U.S.A., 2010, 107, 9170-9175) for fluorescent bacteriophytochrome from Rhodopseudomonas palustris.
钱等人（Science，2009，324，804-807）最近报道了首个红外荧光蛋白（IFP）的创建。它是通过去除 PHY 和组氨酸激酶相关结构域、优化蛋白以防止二聚化以及限制胆绿素构象自由度（尤其是 D 环）从细菌的光敏色素中构建的。我们使用数据库分析和具有自由旋转发色团二面角的分子动力学模拟，对激发态下胆绿素 D 环的可用二面角自由度进行建模，并表明光敏色素中的四吡咯配体是灵活的，可以采用多种构象；然而，它们的构象空间受到蛋白质腔的化学空间特征的限制/定义。我们的模拟证实，与激发态质子转移相关的构象的可及性降低可能是 IFP 产生荧光的原因，正如 Kennis 等人（Proc. Natl. Acad. Sci. U.S.A.，2010，107，9170-9175）所提出的，对于来自沼泽红假单胞菌的荧光细菌光敏色素也是如此。
