Bill E, Haas C, Ding X Q, Maret W, Winkler H, Trautwein A X, Zeppezauer M
Institut für Physik, Medizinische Universität, Lübeck, Federal Republic of Germany.
Eur J Biochem. 1989 Mar 1;180(1):111-21. doi: 10.1111/j.1432-1033.1989.tb14621.x.
The catalytic Zn(II) ion of horse liver alcohol dehydrogenase (EE isozyme) was replaced by Fe(II), providing a novel iron protein with the unusual coordination of Fe(II) to two cysteines residues, one histine residue and water. The electronic structure of iron in this system was characterized by Mössbauer spectroscopy at various temperatures as well as applied magnetic fields and analysed in terms of the spin Hamiltonian formalism. The novelty we found is an unusually weak spin coupling (/J/ less than 0.1 cm-1) of a paramagnet (S = 1) with iron (S = 2). From EPR and biochemical studies we conclude that the corresponding chemical species is triplet oxygen (O2). The quantitative determination of the coupling energy was possible utilizing the competition between Zeemann interaction and spin coupling at weak magnetic fields and low temperature. Oxidation experiments followed by Mössbauer spectroscopy showed that the spin-coupled system is an outer-sphere Fe(II) . (O2)aq complex occurring as an intermediate during a Fe(II)-catalyzed dioxygen activation. We observed two additional Fe(II) species after treatment with O2 and dithionite. The spin Hamiltonian parameters of iron in the coupled system are presented. The results are compared with those of iron in other non-heme iron proteins.
马肝醇脱氢酶（EE同工酶）的催化锌（II）离子被铁（II）取代，从而得到一种新型铁蛋白，其中铁（II）与两个半胱氨酸残基、一个组氨酸残基和水形成异常配位。该体系中铁的电子结构通过在不同温度以及外加磁场下的穆斯堡尔光谱进行表征，并根据自旋哈密顿形式进行分析。我们发现的新奇之处在于顺磁体（S = 1）与铁（S = 2）之间异常弱的自旋耦合（/J/小于0.1 cm-1）。通过电子顺磁共振和生化研究，我们得出相应的化学物种是三线态氧（O2）。利用弱磁场和低温下塞曼相互作用与自旋耦合之间的竞争，可以对耦合能进行定量测定。氧化实验后进行的穆斯堡尔光谱表明，自旋耦合体系是一种外球型Fe（II）.（O2）水合络合物，它是Fe（II）催化双氧活化过程中的一种中间体。在用O2和连二亚硫酸盐处理后，我们观察到另外两种Fe（II）物种。给出了耦合体系中铁的自旋哈密顿参数。并将结果与其他非血红素铁蛋白中铁的结果进行了比较。
