Azotobacter vinelandii nitrogenase

FIGURE 12.4 S = 7/2 EPR of the [8Fe-7S] P-cluster in Azotobacter vinelandii nitrogenase. The experimental spectrum (trace A) has been simulated in the absence (trace B) and the presence (trace C) of D-strain modeled as a correlated distribution in the zero-field parameters D and E. 

Dean, D.R., Setterquist, R.A., Brigle, K.E., Scott, D.J., Laird, N. F., Newton, W.E., (1990) Evidence that conserved residues Cys-62 and Cys-154 within the Azotobacter vinelandii nitrogenase iron-molybdenum protein a-subuflit are essential for nitrogenase activity but conserved residues His-83 and Cys-88 are not. Mol. Microbiol. 4(9),... 

Newton, W. E., Schultz, F. A., Gheller, S. F., Lough, S., McDonald, J. W., Conradson, S. D., Hedman, B., Hodgson, K. O. (1986), Iron-molybdenum cofactor of Azotobacter vinelandii nitrogenase oxidation-reduction properties and structural insights. Polyhedron 5, 567-72. 

Watt, G.D. and Reddy, K.R.N. (1994) Formation of an all ferrous Fe4S4 cluster in the iron protein-component of Azotobacter vinelandii nitrogenase, J. Inorg. Biochem. 53, 281-294. 

W. E. Newton and D. R. Dean, Role of the iron-molybdenum cofactor polypeptide environment in azotobacter vinelandii-nitrogenase catalysis, in Molybdenum Enzymes, Cofactors and Model Systems , eds. E. I. Stiefel, D. Coucouvanis, and... 

A) Preliminary x-ray crystal structure of the Azotobacter vinelandii nitrogenase Fe protein. ... 

FIGURE 16.2 Structure of the FeMo-co of Azotobacter vinelandii nitrogenase, as revealed by the crystallographic work of Rees et al. X may be N ". 

FIGURE 16.3 Structure of the FeMo-co of Azotobacter vinelandii nitrogenase. 

In late 1992 the first crystal structures of the Fe and MoFe proteins of Mo nitrogenase frora Azotobacter vinelandii were published (1-3). 

The nitrogenase proteins are generally characterized by two letters indicating the species and strains of bacteria and the numerals 1 for the MoFe protein and 2 for the Fe protein. Thus, the Fe protein from Azotobacter vinelandii is Av2 and the MoFe protein from Klebsiella pneumoniae is Kpl. 

Fig. 12. The nitrogen fixation genes of Azotobacter vinelandii. This orgEinism has three nitrogenase systems, viz nif, vnf, and anf, which it uses for fixing N2 under different environmental conditions. The boxes with slanted hatching indicate the structural genes of the three systems, those colored dark gray are required for eiU three systems, and those with vertical hatching are required for both the vnf and anf systems.

Although, as indicated in Fig. 12, there is clear genetic evidence for a third nitrogenase in Azotobacter vinelandii, the initial preparations of this enzyme had low activity and contained small quantities of molybdenum as well as iron, and thus the activity might have been... 

Figure 31 X-Ray structure of the active site of Fe-protein in the nitrogenase of Azotobacter vinelandii. Polypeptide chains surround the central Fe4S4 cluster...

Recently, a second or alternative nitrogenase has been isolated from Azotobacter vinelandii (21) and Azotobacter chroococcum (22) that contains vanadium as opposed to molybdenum. The MoFe and VFe nitrogenase proteins from A. vinelandii (called Av and. 4vl , respectively) are known to have different polypeptide structures and it obviously of interest to know to what extent the cluster composition is conserved. Variable temperature MCD studies of the as isolated and thionine oxidized proteins provided a convenient means of addressing this question. 

Georgiadis, M.M., Komiya, H., Chakrabarti, P., Woo, D., Komuc, J.J., Rees, D.C. (1992). Crystallographic structure of the nitrogenase iron protein from Azotobacter Vinelandii. Science 257, 1653-1659. 

The Fe proteins of all three nitrogenases are very similar [1], The Fe protein of Mo nitrogenase is a dimer (Mr —65,000) of equivalent subunits with a single Fe4S4 cluster bound between the subunits by bonds between the cluster Fe atoms and the S atoms of two cysteine residues from each subunit [2], The x-ray crystallographic structure at 0.29 nm resolution of the Fe protein from Azotobacter vinelandii (Av2) has been described (Figure 1) [6], This shows that the Fe4S4... 

The biosynthesis of Fe/S clusters may well proceed via other, possibly more simple Fe/S clusters as intermediates. The products of the genes riifS and nif U in Azotobacter vinelandii are thought to collaborate in nitrogenase metal-locluster biosynthesis NIFS is a sulfide donor NIFU is a [2Fe-2S] protein. The... 

Figure 10.3 Crystallographic structures of the most important iron-sulphur centres in proteins (a) dimeric centre of ferrodoxin from Spinacia oleracea [54], (b) trimeric centre of ferredoxin from Bacillus schlegelii [55], (c) cubane cluster of nitrogenase reductase from Azotobacter vinelandii [56], (d) nitrogenase octameric cluster from Azotobacter vinelandii [57], (e) nitrogenase octameric cluster from Clostridium pasteurianum [58], (f) MoFe cluster of nitrogenase from Azotobacter vinelandii [59], and (g) active centre of sulphite reductase from Escherichia coli [60]...

Strop P,Tatahara PM, Chiu H-J, Angove HC. Crystal structure of the all-ferrous [4Fe-4S]° form of the nitrogenase iron protein from Azotobacter vinelandii. Biochemistry 2001 40 651-6. 

Recently, Brill and co-workers (43, 44) have isolated mutant strains of Azotobacter vinelandii which produce an inactive nitrogenase component. This component can be reactivated by treatment with the neutralized acid-hydrolysis products of other nitrogenases (which themselves become inactive on such a treatment) but not apparently with any other molybdenum enzymes. This may either reflect a difference between the cofactor in nitrogenase and other molybdenum enzymes or may be caused by the reconstitution conditions used which may not have been sufficiently varied to allow for different molybdenum oxidation states to be attained. In any event, the chemical characterization and authentication of the molybdenum cofactor should reveal some of the intimate details of the molybdenum site. 

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