6n4j | pdb_00006n4j

Ti(III)citrate-reduced, nucleotide-free form of the nitrogenase Fe-protein from A. vinelandii

spinqualitylabelsall models 6n4j, resolution 1.95Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 6n4j is a 2 chain structure with sequence from Azotobacter vinelandii. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 1.95Å Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function NIFH1_AZOVI The key enzymatic reactions in nitrogen fixation are catalyzed by the nitrogenase complex, which has 2 components: the iron protein (component 2) and a component 1 which is either a molybdenum-iron protein, a vanadium-iron, or an iron-iron protein.[HAMAP-Rule:MF_00533] Publication Abstract from PubMed The nitrogenase iron protein (Fe-protein) serves as the electron donor for biological nitrogen fixation. Understanding how the Fe-protein controls electron transfer to the active site is critical in addressing the mechanism of substrate reduction. The Fe-protein contains an unusual [4Fe:4S] iron-sulphur cluster that is stable in three oxidation states: 2+, 1+ and 0. Here, we combine structural and spectroscopic techniques, including spatially resolved anomalous dispersion refinement (SpReAD), to report oxidation assignments for individual irons in the cluster for each overall state. Additionally, we report the 1.13-A resolution structure for the Fe-protein with bound ADP, the highest resolution Fe-protein structure presently determined. In the dithionite-reduced [4Fe:4S]1+ state, the SpReAD analysis supports the oxidation state assignment of a delocalized Fe2.5+ pair and a reduced Fe2+ pair. Our work identifies the Fe2.5+ pair as coordinated by the solvent exposed Cys97, while the Fe2+ pair faces the protein interior and is coordinated by Cys132. It is proposed that binding of ATP to the Fe-protein promotes an internal redox rearrangement such that the solvent-exposed Fe becomes reduced, thereby facilitating electron transfer to the nitrogenase molybdenum iron-protein. The SpReAD analysis supports a uniform oxidation state assignment of Fe2+ for all irons in the titanium citrate-reduced [4Fe:4S]0 state, while all irons in the IDS oxidized [4Fe:4S]2+ state are assigned to the valence delocalized Fe2.5+ state. Site-specific oxidation state assignments of the irons in the [4Fe:4S]2+/1+/0 states of the nitrogenase Fe-protein.,Wenke BB, Spatzal T, Rees DC Angew Chem Int Ed Engl. 2019 Jan 30. doi: 10.1002/anie.201813966. PMID:30698901 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Nitrogenase 3D structures

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