Britt R D, Sauer K, Klein M P, Knaff D B, Kriauciunas A, Yu C A, Yu L, Malkin R
Laboratory of Chemical Biodynamics, Lawrence Berkeley Laboratory, Berkeley, California 94720.
Biochemistry. 1991 Feb 19;30(7):1892-901. doi: 10.1021/bi00221a023.
Electron spin echo envelope modulation (ESEEM) experiments performed on the Rieske Fe-S clusters of the cytochrome b6f complex of spinach chloroplasts and of the cytochrome bc1 complexes of Rhodospirillum rubrum, Rhodobacter sphaeroides R-26, and bovine heart mitochondria show modulation components resulting from two distinct classes of 14N ligands. At the g = 1.92 region of the Rieske EPR spectrum of the cytochrome b6f complex, the measured hyperfine couplings for the two classes of coupled nitrogens are A1 = 4.6 MHz and A2 = 3.8 MHz. Similar couplings are observed for the Rieske centers in the three cytochrome bc1 complexes. These ESEEM results indicate a nitrogen coordination environment for these Rieske Fe-S centers that is similar to that of the Fe-S cluster of a bacterial dioxygenase enzyme with two coordinated histidine ligands [Gurbiel, R. J., Batie, C. J., Sivaraja, M., True, A. E., Fee, J. A., Hoffman, B. M., & Ballou, D. P. (1989) Biochemistry 28, 4861-4871]. The Rieske Fe-S cluster lacks modulation components from a weakly coupled peptide nitrogen observed in water-soluble spinach ferredoxin. Treatment with the quinone analogue inhibitor DBMIB causes a shift in the Rieske EPR spectrum to g = 1.95 with no alteration in the magnetic coupling to the two nitrogen atoms. However, the ESEEM pattern of the DBMIB-altered Rieske EPR signal shows evidence of an additional weakly coupled nitrogen similar to that observed in the spinach ferredoxin ESEEM patterns.
对菠菜叶绿体细胞色素b6f复合物以及红螺菌、球形红杆菌R - 26和牛心线粒体的细胞色素bc1复合物中的 Rieske铁硫簇进行的电子自旋回波包络调制（ESEEM）实验表明，调制成分源自两类不同的14N配体。在细胞色素b6f复合物的Rieske EPR谱的g = 1.92区域，两类耦合氮的实测超精细耦合为A1 = 4.6 MHz和A2 = 3.8 MHz。在三种细胞色素bc1复合物的Rieske中心也观察到了类似的耦合。这些ESEEM结果表明，这些Rieske铁硫中心的氮配位环境与一种具有两个配位组氨酸配体的细菌双加氧酶的铁硫簇类似[Gurbiel, R. J., Batie, C. J., Sivaraja, M., True, A. E., Fee, J. A., Hoffman, B. M., & Ballou, D. P. (1989) Biochemistry 28, 4861 - 4871]。Rieske铁硫簇缺乏在水溶性菠菜铁氧还蛋白中观察到的来自弱耦合肽氮的调制成分。用醌类似物抑制剂DBMIB处理会使Rieske EPR谱向g = 1.95移动，而与两个氮原子的磁耦合没有改变。然而，DBMIB改变后的Rieske EPR信号的ESEEM模式显示出存在一个额外的弱耦合氮的证据，这与在菠菜铁氧还蛋白ESEEM模式中观察到的类似。
