Ragsdale S W, Wood H G, Antholine W E
Proc Natl Acad Sci U S A. 1985 Oct;82(20):6811-4. doi: 10.1073/pnas.82.20.6811.
The interaction between carbon monoxide and the CO dehydrogenase from Clostridium thermoaceticum was studied by electron spin resonance (ESR) techniques. When the enzyme reacts with CO, a paramagnetic complex is formed which previously was shown, by isotope substitution, to be due to a nickel-carbon species. In this paper, we demonstrate that iron is also a component of this ESR-detectable complex. When the iron in the enzyme is replaced with 57Fe, a broadening of 18 G in the g parallel and 7 G in the g perpendicular region is seen. This hyperfine interaction is probably due to more than one iron atom in the complex. Coenzyme A influences this ESR spectrum. In the absence of CoA, the ESR spectrum consists of two superimposed signals, which were simulated using the following ESR parameters: signal 1, with g = 2.074 and g = 2.028, and signal 2 with gx = 2.062, gy = 2.047, and gz = 2.028. CoA converts signal 2 into signal 1. Since iron, nickel, and carbon all are part of this ESR-detectable complex, we propose that these atoms exist in a spin-coupled complex with net spin = 1/2, analogous to other iron-sulfur centers in which the metals are bridged by acid-labile sulfide.
利用电子自旋共振（ESR）技术研究了一氧化碳与热醋酸梭菌一氧化碳脱氢酶之间的相互作用。当该酶与一氧化碳反应时，会形成一种顺磁性复合物，通过同位素取代先前已表明，这种复合物是由镍 - 碳物种引起的。在本文中，我们证明铁也是这种可通过ESR检测到的复合物的一个组分。当酶中的铁被(^{57}Fe)取代时，在g平行区域观察到18 G的谱线增宽，在g垂直区域观察到7 G的谱线增宽。这种超精细相互作用可能是由于复合物中有不止一个铁原子。辅酶A会影响这种ESR谱。在没有辅酶A的情况下，ESR谱由两个叠加信号组成，使用以下ESR参数进行模拟：信号1，(g = 2.074)和(g = 2.028)，信号2，(g_x = 2.062)，(g_y = 2.047)，(g_z = 2.028)。辅酶A将信号2转化为信号1。由于铁、镍和碳都是这种可通过ESR检测到的复合物的一部分，我们提出这些原子存在于一个净自旋( = 1/2)的自旋耦合复合物中，类似于其他金属由酸不稳定硫化物桥连的铁 - 硫中心。
