Characterization of isolated nitrogenase FeVco.
The cofactors of the Mo- and V-nitrogenases (i.e., FeMoco and FeVco) are homologous metal centers with distinct catalytic properties. So far, there has been only one report on the isolation of FeVco from Azotobacter chroococcum. However, this isolated FeVco species did not carry the full substrate-reducing capacity, as it is unable to restore the N(2)-reducing ability of the cofactor-deficient MoFe protein. Here, we report the isolation and characterization of a fully active species of FeVco from A. vinelandii. Our metal and activity analyses show that FeVco has been extracted intact, carrying with it the characteristic capacity to reduce C(2)H(2) to C(2)H(6) and, perhaps even more importantly, the ability to reduce N(2) to NH(3). Moreover, our EPR and XAS/EXAFS investigations indicate that FeVco is similar to, yet distinct from FeMoco in electronic properties and structural topology, which could account for the differences in the reactivity of the two cofactors. The outcome of this study not only permits the proposal of the first EXAFS-based structural model of the isolated FeVco but also lays a foundation for future catalytic and structural investigations of this unique metallocluster.
Fay
Aaron W
AW
Department of Molecular Biology and Biochemistry, University of California, Irvine, California 92697, USA.
Blank
Michael A
MA
Lee
Chi Chung
CC
Hu
Yilin
Y
Hodgson
Keith O
KO
Hedman
Britt
B
Ribbe
Markus W
MW
D000114:Acetylene / Q000737:chemistry; D000641:Ammonia / Q000138:chemical synthesis / Q000737:chemistry; D001395:Azotobacter / Q000201:enzymology; D055162:Biocatalysis; D018360:Crystallography, X-Ray; D004980:Ethane / Q000138:chemical synthesis / Q000737:chemistry; D008958:Models, Molecular; D008982:Molybdenum / Q000737:chemistry / Q000378:metabolism*; D009584:Nitrogen / Q000737:chemistry; D009591:Nitrogenase / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D013379:Substrate Specificity; D014639:Vanadium / Q000737:chemistry / Q000378:metabolism*
D014639:Vanadium; D000641:Ammonia; D008982:Molybdenum; D009591:Nitrogenase; D004980:Ethane; D009584:Nitrogen; D000114:Acetylene