Redox-dependent structural changes in the nitrogenase P-cluster
Redox-dependent structural changes in the nitrogenase P-cluster
复制标题
DOI：
10.1021/bi9626665
复制
发表时间：
1997-02-11
期刊：
影响因子：
2.9
通讯作者：
Rees, DC
中科院分区：
文献类型：
--
作者：
Peters, JW;Stowell, MHB;Rees, DC
在两种氧化态下，固氮菌的mfe蛋白的结构被细化到2.0埃的分辨率。晶体的EPR研究表明，结构对应于光谱分配的氧化（p(OX)/M-OX）和天然或二硫代还原（p - n /M-N）形式的酶，两种mofe -蛋白结构基本相同，除了p -簇。每种状态下的mofe蛋白p簇都含有8个铁原子和7个S原子。两种氧化还原态之间的相互转化涉及两个铁原子的运动和由中心S原子提供配体的蛋白质配位交换。在氧化的P-OX状态下，该蛋白通过6个半胱氨酸配体、ser - β 188 O γ和cys - α 88的主酰胺来协调该簇。在天然的P-N态下，ser - β 188 O γ和cys - α 88的酰胺N由于它们的配位铁原子向中心硫的移动而不再配位。因此，这个中心硫采用了一个扭曲的八面体环境，周围有六个铁原子。先前描述的含有8Fe-8S的p -团簇模型可能反映了将单一结构建模为这两种p -团簇氧化还原态的混合物的不适当。这些观察到的氧化还原介导的p -团簇结构变化表明，该团簇在氮酶中耦合电子转移和质子转移中起作用。
The structure of the nitrogenase MoFe-protein from Azotobacter vinelandii has been refined to 2.0 Angstrom resolution in two oxidation states. EPR studies on the crystals indicate that the structures correspond to the spectroscopically assigned oxidized (p(OX)/M-OX) and the native or dithionite-reduced (P-N/M-N) forms of the enzyme, Both MoFe-protein structures are essentially identical, with the exception of the P-cluster. The MoFe-protein P-cluster in each state is found to contain eight Fe and seven S atoms. Interconversion between the two redox states involves movement of two Fe atoms and an exchange of protein coordination for ligands supplied by a central S atom. In the oxidized P-OX state, the cluster is coordinated by the protein through six cysteine ligands, Ser-beta 188 O gamma, and the backbone amide of Cys-alpha 88. In the native P-N state, Ser-beta 188 O gamma and the amide N of Cys-alpha 88 no longer coordinate the cluster due to movement of their coordinated Fe atoms toward the central sulfur. Consequently, this central sulfur adopts a distorted octahedral environment with six surrounding Fe atoms. A previously described model of the P-cluster containing 8Fe-8S likely reflects the inappropriate modeling of a single structure to a mixture of these two P-cluster redox states, These observed redox-mediated structural changes of the P-cluster suggest a role for this cluster in coupling electron transfer and proton transfer in nitrogenase.