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 PubMedNitrogenase catalyzes the ATP-dependent reduction of dinitrogen to ammonia during the process of biological nitrogen fixation that is essential for sustaining life. The active site FeMo-cofactor contains a [7Fe:1Mo:9S:1C] metallocluster coordinated with an R-homocitrate (HCA) molecule. Here, we establish through single particle cryoEM and chemical analysis of two forms of the Azotobacter vinelandii MoFe-protein - a high pH turnover inactivated species and a âNifV variant that cannot synthesize HCA - that loss of HCA is coupled to alpha-subunit domain and FeMo-cofactor disordering, and formation of a histidine coordination site. We further find a population of the âNifV variant complexed to an endogenous protein identified through structural and proteomic approaches as the uncharacterized protein NafT. Recognition by endogenous NafT demonstrates the physiological relevance of the HCA-compromised form, perhaps for cofactor insertion or repair. Our results point towards a dynamic active site in which HCA plays a role in enabling nitrogenase catalysis by facilitating activation of the FeMo-cofactor from a relatively stable form to a state capable of reducing dinitrogen under ambient conditions. Structural consequences of turnover-induced homocitrate loss in nitrogenase.,Warmack RA, Maggiolo AO, Orta A, Wenke BB, Howard JB, Rees DC Nat Commun. 2023 Feb 25;14(1):1091. doi: 10.1038/s41467-023-36636-4. PMID:36841829[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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