期刊
CHEMBIOCHEM
卷 21, 期 12, 页码 1742-1748出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/cbic.201900654
关键词
ammonia formation; citrate; nitrogenases; vanadium; V cluster
资金
- DOE (BES) [DE-SC0016510, DE-SC0014470]
- U.S. Department of Energy (DOE) [DE-SC0014470, DE-SC0016510] Funding Source: U.S. Department of Energy (DOE)
Nitrogenases catalyze the ambient reduction of N-2 and CO at its cofactor site. Herein we present a biochemical and spectroscopic characterization of an Azotobacter vinelandii V nitrogenase variant expressing a citrate-substituted cofactor. Designated VnfDGK(Cit), the catalytic component of this V nitrogenase variant has an alpha beta(2)(delta) subunit composition and carries an 8Fe P* cluster and a citrate-substituted V cluster analogue in the alpha beta dimer, as well as a 4Fe cluster in the orphaned beta-subunit. Interestingly, when normalized based on the amount of cofactor, VnfDGK(Cit) shows a shift of N-2 reduction from H-2 evolution toward NH3 formation and an opposite shift of CO reduction from hydrocarbon formation toward H-2 evolution. These observations point to a role of the organic ligand in proton delivery during catalysis and imply the use of different reaction sites/mechanisms by nitrogenase for different substrate reductions. Moreover, the increased NH3/H-2 ratio upon citrate substitution suggests the possibility to modify the organic ligand for improved ammonia synthesis in the future.
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