Chan M K, Kim J, Rees D C
Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena 91125.
Science. 1993 May 7;260(5109):792-4. doi: 10.1126/science.8484118.
Structures recently proposed for the FeMo-cofactor and P-cluster pair of the nitrogenase molybdenum-iron (MoFe)-protein from Azotobacter vinelandii have been crystallographically verified at 2.2 angstrom resolution. Significantly, no hexacoordinate sulfur atoms are observed in either type of metal center. Consequently, the six bridged iron atoms in the FeMo-cofactor are trigonally coordinated by nonprotein ligands, although there may be some iron-iron bonding interactions that could provide a fourth coordination interaction for these sites. Two of the cluster sulfurs in the P-cluster pair are very close together (approximately 2.1 angstroms), indicating that they form a disulfide bond. These findings indicate that a cavity exists in the interior of the FeMo-cofactor that could be involved in substrate binding and suggest that redox reactions at the P-cluster pair may be linked to transitions of two cluster-bound sulfurs between disulfide and sulfide oxidation states.
最近提出的来自棕色固氮菌的固氮酶钼铁（MoFe）蛋白的铁钼辅因子和P簇对的结构已在2.2埃分辨率下通过晶体学验证。值得注意的是，在任何一种金属中心都未观察到六配位硫原子。因此，铁钼辅因子中的六个桥连铁原子由非蛋白质配体进行三角配位，尽管可能存在一些铁 - 铁键相互作用，可为这些位点提供第四种配位相互作用。P簇对中的两个簇硫非常靠近（约2.1埃），表明它们形成了二硫键。这些发现表明铁钼辅因子内部存在一个可能参与底物结合的腔，并表明P簇对处的氧化还原反应可能与两个簇结合硫在二硫键和硫化物氧化态之间的转变有关。
