How proteins trigger excitation energy transfer in the FMO complex of green sulfur bacteria
How proteins trigger excitation energy transfer in the FMO complex of green sulfur bacteria
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DOI：
10.1529/biophysj.105.079483
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发表时间：
2006-10-01
影响因子：
3.4
通讯作者：
Renger, Thomas
中科院分区：
文献类型：
--
作者：
Adolphs, Julia;Renger, Thomas
本文提出了一种简单的计算蛋白质环境中色素光学跃迁能的静电方法，并将其应用于无氯原虫与三氯甲烷的Fenna-Matthews-Olson(FMO)络合物。这种方法首次允许我们在实验光谱和基于颜料跃迁能的计算之间达成一致，这些跃迁能在很大程度上是独立计算的，而不是与光谱拟合。这样，就有可能理解蛋白质触发激发能量转移反应的分子机制。假设蛋白质的标准质子化模式，并考虑了三种不同的配体类型，通过计算带电氨基酸引起的电致变色位移，得到了aestuarii和C.tepiumFMO复合体的七种细菌叶绿素a色素的激发能相对位移。这些计算解释了由光谱拟合得到的跃迁能的一些早期结果。此外，通过使用更先进的光谱理论、遗传算法和从考虑介电蛋白质环境影响的静电计算中获得的激子耦合，验证了这些早期的拟合。这两个独立的位置能量计算强烈支持FMO三聚体相对于光合膜的两种可能取向之一，这两种取向被电子显微镜研究和线性二向色性实验所证实。要有效地将激发能转移到反应中心，需要将细菌叶绿素3和4作为连接物颜料。通过FMO复合体的激发能量的时间和空间转移被计算为沿着两个分支进行，转移时间相差一个数量级。
A simple electrostatic method for the calculation of optical transition energies of pigments in protein environments is presented and applied to the Fenna-Matthews-Olson (FMO) complex of Prosthecochloris aestuarii and Chlorobium tepidum. The method, for the first time, allows us to reach agreement between experimental optical spectra and calculations based on transition energies of pigments that are calculated in large part independently, rather than fitted to the spectra. In this way it becomes possible to understand the molecular mechanism allowing the protein to trigger excitation energy transfer reactions. The relative shift in excitation energies of the seven bacteriochlorophyll-a pigments of the FMO complex of P. aestuarii and C. tepidum are obtained from calculations of electrochromic shifts due to charged amino acids, assuming a standard protonation pattern of the protein, and by taking into account the three different ligand types of the pigments. The calculations provide an explanation of some of the earlier results for the transition energies obtained from fits of optical spectra. In addition, those earlier fits are verified here by using a more advanced theory of optical spectra, a genetic algorithm, and excitonic couplings obtained from electrostatic calculations that take into account the influence of the dielectric protein environment. The two independent calculations of site energies strongly favor one of the two possible orientations of the FMO trimer relative to the photosynthetic membrane, which were identified by electron microscopic studies and linear dichroism experiments. Efficient transfer of excitation energy to the reaction center requires bacteriochlorophylls 3 and 4 to be the linker pigments. The temporal and spatial transfer of excitation energy through the FMO complex is calculated to proceed along two branches, with transfer times that differ by an order of magnitude.