Electron transfer from copper to heme within the methylamine dehydrogenase-amicyanin-cytochrome c-551i complex
Electron transfer from copper to heme within the methylamine dehydrogenase-amicyanin-cytochrome c-551i complex
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DOI：
10.1021/bi952854f
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发表时间：
1996-06-25
期刊：
影响因子：
2.9
通讯作者：
Jones, LH
中科院分区：
文献类型：
--
作者：
Davidson, VL;Jones, LH
甲胺脱氢酶（MADH）、amicyanin和细胞色素c-551 i是可溶性氧化还原蛋白，其在溶液中形成复合物[Chen，L.，杜利河马修斯，F.美国，& Davidson，V. L.（1994）Science 264，86-90]，其是从MADH的色氨酸蒽醌辅因子经由胺花青苷的铜中心向血红素的生理电子转移所需的。通过瞬态动力学和热力学分析，研究了蛋白质络合物中铜离子向血红素的电子转移反应。在30 ℃时，该电子转移反应的速率为87 s（-1），并随温度而变化。该反应的重组能（λ）为1.1 eV，电子耦合（H-AB）为0.3 cm（-1）。这些分析的结果还预测电子转移距离为13-24埃，这取决于所使用的β值。较大的值接近在络合物的晶体结构中观察到的直接铜至血红素距离。最有效的电子转移的途径进行了预测，从晶体结构使用Greenpath程序，这些预测与电子转移反应的解决方案研究的结果。它的结论是，电子转移，事实上，所观察到的电子转移反应在溶液中的速率限制和两个氧化还原中心强烈耦合，给定的距离将它们分开。
Methylamine dehydrogenase (MADH), amicyanin, and cytochrome c-551i are soluble redox proteins that form a complex in solution [Chen, L., Durley, R., Mathews, F. S., & Davidson, V. L. (1994) Science 264, 86-90] which is required for the physiologic electron transfer from the tryptophan tryptophylquinone cofactor of MADH to heme via the copper center of amicyanin. The electron transfer reaction from copper to heme within the protein Complex has been characterized by transient kinetic and thermodynamic analysis. The rate of this electron transfer reaction is 87 s(-1) at 30 degrees C land it varied with temperature. The reaction exhibited a reorganizational energy (lambda) of 1.1 eV and an electronic coupling (H-AB) of 0.3 cm(-1). The results of these analyses also predict an electron transfer distance, depending upon the value of beta which is used, of 13-24 Angstrom. The larger value approximates the direct copper to heme distance observed in the crystal structure of the complex. The most efficient pathways for electron transfer were predicted from the crystal structure using the Greenpath program, and these predictions were correlated with the results of the solution studies of the electron transfer reaction. It is concluded that electron transfer is, in fact, rate limiting for the observed electron transfer reaction in solution and that the two redox centers are strongly coupled, given the distance which separates them.