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Belinda B. Wenke Thomas Spatzal Douglas C. Rees 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(12):3934-3937
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]1+ state, our analysis identifies a solvent exposed, delocalized Fe2.5+ pair and a buried Fe2+ 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]0 and [4Fe:4S]2+ states, the SpReAD analysis supports oxidation states assignments for all irons in these clusters of Fe2+ and valence delocalized Fe2.5+, respectively. 相似文献
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Andrew J. Jasniewski Jarett Wilcoxen Kazuki Tanifuji Britt Hedman Keith O. Hodgson R. David Britt Yilin Hu Markus W. Ribbe 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(41):14845-14849
Nitrogenases catalyze the reduction of N2 to NH4+ at its cofactor site. Designated the M‐cluster, this [MoFe7S9C(R‐homocitrate)] cofactor is synthesized via the transformation of a [Fe4S4] cluster pair into an [Fe8S9C] precursor (designated the L‐cluster) prior to insertion of Mo and homocitrate. We report the characterization of an eight‐iron cofactor precursor (designated the L*‐cluster), which is proposed to have the composition [Fe8S8C] and lack the “9th sulfur” in the belt region of the L‐cluster. Our X‐ray absorption and electron spin echo envelope modulation (ESEEM) analyses strongly suggest that the L*‐cluster represents a structural homologue to the l ‐cluster except for the missing belt sulfur. The absence of a belt sulfur from the L*‐cluster may prove beneficial for labeling the catalytically important belt region, which could in turn facilitate investigations into the reaction mechanism of nitrogenases. 相似文献
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Gan Xu Jie Zhou Zheng Wang Richard H. Holm Xu‐Dong Chen 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(46):16621-16625
Incorporation of monatomic 2p ligands into the core of iron–sulfur clusters has been researched since the discovery of interstitial carbide in the FeMo cofactor of Mo‐dependent nitrogenase, but has proven to be a synthetic challenge. Herein, two distinct synthetic pathways are rationalized to install nitride ligands into targeted positions of W‐Fe‐S clusters, generating unprecedented nitride‐ligated iron–sulfur clusters, namely [(Tp*)2W2Fe6(μ4‐N)2S6L4]2? (Tp*=tris(3,5‐dimethyl‐1‐pyrazolyl)hydroborate(1?), L=Cl? or Br?). 57Fe Mössbauer study discloses metal oxidation states of WIV2FeII4FeIII2 with localized electron distribution, which is analogous to the mid‐valent iron centres of FeMo cofactor at resting state. Good agreement of Mössbauer data with the empirical linear relationship for Fe–S clusters indicates similar ligand behaviour of nitride and sulfide in such clusters, providing useful reference for reduced nitrogen in a nitrogenase‐like environment. 相似文献
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Mengxuan Jia Sambuddha Sen Christine Wachnowsky Insiya Fidai Prof. James A. Cowan Prof. Vicki H. Wysocki 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(17):6790-6794
Many iron–sulfur proteins involved in cluster trafficking form [2Fe–2S]-cluster-bridged complexes that are often challenging to characterize because of the inherent instability of the cluster at the interface. Herein, we illustrate the use of fast, online buffer exchange coupled to a native mass spectrometry (OBE nMS) method to characterize [2Fe–2S]-cluster-bridged proteins and their transient cluster-transfer intermediates. The use of this mechanistic and protein-characterization tool is demonstrated with holo glutaredoxin 5 (GLRX5) homodimer and holo GLRX5:BolA-like protein 3 (BOLA3) heterodimer. Using the OBE nMS method, cluster-transfer reactions between the holo-dimers and apo-ferredoxin (FDX2) are monitored, and intermediate [2Fe–2S] species, such as (FDX2:GLRX5:[2Fe–2S]:GSH) and (FDX2:BOLA3:GLRX5:[2Fe–2S]:GSH) are detected. The OBE nMS method is a robust technique for characterizing iron–sulfur-cluster-bridged protein complexes and transient iron–sulfur-cluster transfer intermediates. 相似文献
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