Spangler N J, Lindahl P A, Bandarian V, Ludden P W
Department of Biochemistry, College of Agricultural and Life Sciences, University of Wisconsin, Madison, Wisconsin 53706, USA.
J Biol Chem. 1996 Apr 5;271(14):7973-7. doi: 10.1074/jbc.271.14.7973.
Carbon-monoxide dehydrogenase (CODH) from Rhodospirillum rubrum contains two metal centers: a Ni-X-[Fe4S4]2+/1+ cluster (C-center) that serves as the COoxidation site and a standard [Fe4S4]2+/1+ cluster (B-center) that mediates electron flow from the C-center to external electron acceptors. Four states of the C-center were previously identified in electron paramagnetic resonance (EPR) and Mössbauer studies. In this report, EPR-redox titrations demonstrate that the fully oxidized, diamagnetic form of the C-center (Cox) undergoes a one-electron reduction to the Cred1 state (gav = 1.87) with a midpoint potential of -110 mV. The reduction of Cox to Cred1 is shown to coincide with the reduction of an [Fe4S4]2+/1+ cluster in redox-titration experiments monitored by UV-visible spectroscopy. Nickel-deficient CODH, which is devoid of nickel yet contains both [Fe4S4]2+/1+ clusters, does not exhibit EPR-active states or reduced Fe4S4 clusters at potentials more positive than -350 mV.
来自红螺菌的一氧化碳脱氢酶（CODH）含有两个金属中心：一个作为CO氧化位点的Ni-X-[Fe4S4]2+/1+簇（C中心）和一个介导电子从C中心流向外部电子受体的标准[Fe4S4]2+/1+簇（B中心）。先前在电子顺磁共振（EPR）和穆斯堡尔研究中确定了C中心的四种状态。在本报告中，EPR氧化还原滴定表明，C中心的完全氧化、抗磁性形式（Cox）经历单电子还原为Cred1状态（gav = 1.87），中点电位为-110 mV。在紫外可见光谱监测的氧化还原滴定实验中，Cox还原为Cred1与[Fe4S4]2+/1+簇的还原同时发生。缺乏镍但含有两个[Fe4S4]2+/1+簇的缺镍CODH在电位高于-350 mV时不表现出EPR活性状态或还原的Fe4S4簇。
