Establishment of Determining Method of Electron Transfer Pathway in Pnoteins and Production of Pathway Map

蛋白质中的电子传递是线粒体光合作用和呼吸作用能量转导的重要反应。这种电子转移是通过隧穿效应发生的。隧道通路中使用了蛋白质的哪一部分以及如何通过通道调节来调节电子传递速率是一个重要的问题。确定蛋白质中电子传递途径的理论研究一直是我们实验室的主要课题。自1998年以来。作为这项研究的一个原则，我们的目标是做理论计算来反映蛋白质的真实结构，而不是从现象学上对待它们。为此，我们通过量子化学计算获得了整个蛋白质的电子态，并试图通过深入考虑的理论操作确定简单的电子转移途径。我们为这些计算买了一台高速工作站。作为一种典型的蛋白质，我们在位点定向诱变中任意引入的嘌呤残基上处理了Ru络合物修饰的azurins。我们计算了从供体到受体的所有原子间的隧穿电流。我们用箭头把它们画在蛋白质的图上。此外，用新开发的统计方法对电流进行平均，得到了蛋白质的平均隧道区域图。由于它看起来像缠绕的蠕虫，我们把这个分析称为蠕虫模型。该模型的出发点与Beratan和Onuchic之前提出的路径模型非常相似。但它的最终形式与达顿假设的直线形式相当相似。也就是说，蠕虫模型整合了迄今为止被认为是完全不同的两种模型。下一步，我们应用蠕虫模型分析细胞色素c氧化酶的电子隧穿途径。它的研究正在进行中。

Electron transfer in proteins is a very important reaction in energy transduction of photosynthesis and respiration in mitochondria. This electron transfer takes place by the tunneling effect. It is an important problem which part of the protein is used in the tunneling pathway and how the regulation of electron transfer rate is made through the pathway regulation.The theoretical study for determining the electron transfer pathway in proteins has been the main thema in our lab. since 1998. As a plinciple of the study, we aimed to do theoretical calculations reflecting the real structure of proteins without treating them phenomenologically. For this purpose, we obtained the electronic state of the whole protein by the quantum chemical calculations and tried to determine simple electron transfer pathway by an deeply considered theoretical manipulation. We bought a high speed workstation for these calculations. As a typical proteins, we treated azurins modified by the Ru complex at the hystidine residue which was arbitraily introduced by the site-directed mutagenesis. We calculated all the inter atom-atom turnneling currents passing from donor to acceptor. We drew them in the picture of protein by arrows. Furthermore, averaging the currents by the newly developed statistical method, we obtained a picure of averaged tunneling rgion in proteins. Since it looked like winding worm, we called this analysis worm model. The starting point of this model is quite similar to the pathway model previously proposed by Beratan and Onuchic. But its final form is rather similar to the straight one as assumed by Dutton. Namely, the worm model consolidates the two models which were so far considered as quite different models.As a next step, we apply the worm model for the analysis of the electron tunneling pathway of cytochrome c oxidase. Its study is on the way.