Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA, 91125, USA.
Howard Hughes Medical Institute, California Institute of Technology, Pasadena, CA, 91125, USA.
Angew Chem Int Ed Engl. 2019 Mar 18;58(12):3894-3897. doi: 10.1002/anie.201813966. Epub 2019 Feb 14.
The nitrogenase iron protein (Fe-protein) contains an unusual [4Fe:4S] iron-sulphur cluster that is stable in three oxidation states: 2+, 1+, and 0. Here, we use spatially resolved anomalous dispersion (SpReAD) refinement to determine oxidation assignments for the individual irons for each state. Additionally, we report the 1.13-Å resolution structure for the ADP bound Fe-protein, the highest resolution Fe-protein structure presently determined. In the dithionite-reduced [4Fe:4S] state, our analysis identifies a solvent exposed, delocalized Fe pair and a buried Fe pair. We propose that ATP binding by the Fe-protein promotes an internal redox rearrangement such that the solvent-exposed Fe pair becomes reduced, thereby facilitating electron transfer to the nitrogenase molybdenum iron-protein. In the [4Fe:4S] and [4Fe:4S] states, the SpReAD analysis supports oxidation states assignments for all irons in these clusters of Fe and valence delocalized Fe , respectively.
固氮酶铁蛋白（Fe 蛋白）含有一个不寻常的 [4Fe:4S] 铁-硫簇，它在三种氧化态下稳定：2+、1+和 0。在这里，我们使用空间分辨反常分散（SpReAD）精修来确定每个状态下各个铁的氧化分配。此外，我们还报告了 ADP 结合 Fe 蛋白的 1.13-Å 分辨率结构，这是目前确定的最高分辨率 Fe 蛋白结构。在连二亚硫酸盐还原的 [4Fe:4S] 状态下，我们的分析确定了一个暴露在溶剂中的、离域的 Fe 对和一个埋藏的 Fe 对。我们提出，Fe 蛋白与 ATP 的结合促进了内部氧化还原重排，使得暴露在溶剂中的 Fe 对被还原，从而促进电子向氮酶钼铁蛋白的转移。在 [4Fe:4S] 和 [4Fe:4S] 状态下，SpReAD 分析分别支持这些 Fe 簇和价离域 Fe 簇中所有铁的氧化态分配。
