Banci L, Bertini I, Huber J G, Spyroulias G A, Turano P
Department of Chemistry, University of Florence, Italy.
J Biol Inorg Chem. 1999 Feb;4(1):21-31. doi: 10.1007/s007750050285.
In the frame of a broad study on the structural differences between the two redox forms of cytochromes to be related to the electron transfer process, the NMR solution structure of horse heart cytochrome c in the reduced form has been determined. The structural data obtained in the present work are compared to those already available in the literature on the same protein and the presence of conformational differences is discussed in the light of the experimental method employed for the structure determination. Redox-state dependent changes are analyzed and in particular they are related to the role of propionate-7 of the heme. Also some hydrogen bonds are changed upon reduction of the heme iron. A substantial similarity is observed for the backbone fold, independently of the oxidation state. At variance, some meaningful differences are observed in the orientation of a few side chains. These changes are related to those found in the case of the highly homologous cytochrome c from Saccharomyces cerevisiae. The exchangeability of the NH protons has been investigated and found to be smaller than in the case of the oxidized protein. We think that this is a characteristic of reduced cytochromes and that mobility is a medium for molecular recognition in vivo.
在一项关于细胞色素两种氧化还原形式之间结构差异与电子转移过程关系的广泛研究框架内，已确定了还原态马心细胞色素c的核磁共振溶液结构。将本研究中获得的结构数据与文献中已有的关于同一蛋白质的数据进行比较，并根据用于结构测定的实验方法讨论构象差异的存在。分析了氧化还原状态依赖性变化，特别是它们与血红素丙酸酯-7的作用相关。血红素铁还原时，一些氢键也会发生变化。无论氧化态如何，主链折叠都存在很大的相似性。不同的是，在一些侧链的取向上观察到了一些有意义的差异。这些变化与酿酒酵母中高度同源的细胞色素c的情况中发现的变化有关。对NH质子的交换性进行了研究，发现其比氧化态蛋白质的情况要小。我们认为这是还原态细胞色素的一个特征，并且流动性是体内分子识别的一种媒介。
