Structural highlights
FunctionNIFD_AZOVI This molybdenum-iron protein is part of the nitrogenase complex that catalyzes the key enzymatic reactions in nitrogen fixation. Publication Abstract from PubMedDinitrogen reduction in the biological nitrogen cycle is catalyzed by nitrogenase, a two-component metalloenzyme. Understanding of the transformation of the inert resting state of the active site FeMo-cofactor into an activated state capable of reducing dinitrogen remains elusive. Here we report the catalysis dependent, site-selective incorporation of selenium into the FeMo-cofactor from selenocyanate as a newly identified substrate and inhibitor. The 1.60 A resolution structure reveals selenium occupying the S2B site of FeMo-cofactor in the Azotobacter vinelandii MoFe-protein, a position that was recently identified as the CO-binding site. The Se2B-labeled enzyme retains substrate reduction activity and marks the starting point for a crystallographic pulse-chase experiment of the active site during turnover. Through a series of crystal structures obtained at resolutions of 1.32-1.66 A, including the CO-inhibited form of Av1-Se2B, the exchangeability of all three belt-sulfur sites is demonstrated, providing direct insights into unforeseen rearrangements of the metal center during catalysis. Catalysis-dependent selenium incorporation and migration in the nitrogenase active site iron-molybdenum cofactor.,Spatzal T, Perez KA, Howard JB, Rees DC Elife. 2015 Dec 16;4. pii: e11620. doi: 10.7554/eLife.11620. PMID:26673079[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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