Electron Transfer Tunneling Pathways in Bovine Heart Cytochrome c Oxidase

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• 作者：Dmitry M. Medvedev ; Iraj Daizadeh ; and Alexei A. Stuchebrukhov
• 刊名：Journal of the American Chemical Society
• 出版年：2000
• 出版时间：July 19, 2000
• 年：2000
• 卷：122
• 期：28
• 页码：6571 - 6582
• 全文大小：420K
• 年卷期：v.122,no.28(July 19, 2000)
• ISSN：1520-5126

文摘

Results of a study of internal electron transfer in bovine heart cytochrome c oxidase with the methodof tunneling currents are presented. Electronic structure of the protein complex is treated at the semiempiricalextended Hückel level. Two distinct pathways connecting Cu_A and heme a are found, one of them is similarto proposed earlier in the literature, the other is new. The pathway connecting heme a and heme a₃ is alsoidentified. This pathway differs from those proposed before. The calculated reaction rates between Cu_A andFe_a and between Fe_a and Fe_a3 are in reasonable agreement with experimental data. The tunneling matrix elementfor electron transfer from Cu_A to the binuclear site is found to be very small, which is consistent withexperimental evidence of the absence of this reaction. With the assumption that evolution places constraintson functionally important amino acids, we suggest that amino acids implicated in the electron-transfer pathwayswill show a high degree of conservation in different organisms. Sequence analysis performed on subunit I andII revealed that this is indeed the case; amino acids of the identified tunneling pathways showed very littleevolutionary variability.