6o7o

Nitrogenase MoFeP mutant F99Y/S188A from Azotobacter vinelandii in the dithionite reduced state after redox cycling

spinqualitylabelsall models 6o7o, resolution 1.89Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 6o7o is a 4 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 1.89Å Ligands: FE, HCA Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function NIFD_AZOVI This molybdenum-iron protein is part of the nitrogenase complex that catalyzes the key enzymatic reactions in nitrogen fixation. Publication Abstract from PubMed Molybdenum nitrogenase catalyzes the reduction of dinitrogen into ammonia, which requires the coordinated transfer of eight electrons to the active site cofactor (FeMoco) through the intermediacy of an [8Fe-7S] cluster (P-cluster), both housed in the molybdenum-iron protein (MoFeP). Previous studies on MoFeP from two different organisms, Azotobacter vinelandii ( Av) and Gluconacetobacter diazotrophicus ( Gd), have established that the P-cluster is conformationally flexible and can undergo substantial structural changes upon two-electron oxidation to the P(OX) state, whereby a backbone amidate and an oxygenic residue (Ser or Tyr) ligate to two of the cluster's Fe centers. This redox-dependent change in coordination has been implicated in the conformationally gated electron transfer in nitrogenase. Here, we have investigated the role of the oxygenic ligand in Av MoFeP, which natively contains a Ser ligand (betaSer188) to the P-cluster. Three variants were generated in which (1) the oxygenic ligand was eliminated (betaSer188Ala), (2) the P-cluster environment was converted to the one in Gd MoFeP (betaPhe99Tyr/betaSer188Ala), and (3) two oxygenic ligands were simultaneously included (betaPhe99Tyr). Our studies have revealed that the P-cluster can become compositionally labile upon oxidation and reversibly lose one or two Fe centers in the absence of the oxygenic ligand, while still retaining wild-type-like dinitrogen reduction activity. Our findings also suggest that Av and Gd MoFePs evolved with specific preferences for Ser and Tyr ligands, respectively, and that the structural control of these ligands must extend beyond the primary and secondary coordination spheres of the P-cluster. The P-cluster adds to the increasing number of examples of inherently labile Fe-S clusters whose compositional instability may be an obligatory feature to enable redox-linked conformational changes to facilitate multielectron redox reactions. Redox-Dependent Metastability of the Nitrogenase P-Cluster.,Rutledge HL, Rittle J, Williamson LM, Xu WA, Gagnon DM, Tezcan FA J Am Chem Soc. 2019 Jun 13. doi: 10.1021/jacs.9b04555. PMID:31146522 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Nitrogenase 3D structures

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