Wang Sufan, Smith Sean C
Centre for Computational Molecular Science, Chemistry Building #68, The University of Queensland, Brisbane, Queensland 4072, Australia.
J Phys Chem B. 2006 Mar 16;110(10):5084-93. doi: 10.1021/jp056966k.
We explore several models for the ground-state proton chain transfer pathway between the green fluorescent protein chromophore and its surrounding protein matrix, with a view to elucidating mechanistic aspects of this process. We have computed quantum chemically the minimum energy pathways (MEPs) in the ground electronic state for one-, two-, and three-proton models of the chain transfer. There are no stable intermediates for our models, indicating that the proton chain transfer is likely to be a single, concerted kinetic step. However, despite the concerted nature of the overall energy profile, a more detailed analysis of the MEPs reveals clear evidence of sequential movement of protons in the chain. The ground-state proton chain transfer does not appear to be driven by the movement of the phenolic proton off the chromophore onto the neutral water bridge. Rather, this proton is the last of the three protons in the chain to move. We find that the first proton movement is from the bridging Ser205 moiety to the accepting Glu222 group. This is followed by the second proton moving from the bridging water to the Ser205--for our model this is where the barrier occurs. The phenolic proton on the chromophore is hence the last in the chain to move, transferring to a bridging "water" that already has substantial negative charge.
我们探究了绿色荧光蛋白发色团与其周围蛋白质基质之间基态质子链转移途径的几种模型，旨在阐明这一过程的机制方面。我们已经通过量子化学计算了链转移的单质子、双质子和三质子模型在基态电子态下的最小能量途径（MEP）。我们的模型没有稳定的中间体，这表明质子链转移可能是一个单一的、协同的动力学步骤。然而，尽管整体能量分布具有协同性质，但对MEP的更详细分析揭示了链中质子顺序移动的明确证据。基态质子链转移似乎不是由酚质子从发色团转移到中性水桥上驱动的。相反，这个质子是链中三个质子中最后一个移动的。我们发现第一个质子从桥连的Ser205部分转移到接受质子的Glu222基团。接着第二个质子从桥连水转移到Ser205——对于我们的模型来说，这是势垒出现的位置。因此，发色团上酚质子是链中最后一个移动的，转移到已经带有大量负电荷的桥连“水”上。
