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

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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.