Azotobacter properties

Pierik, A.J., Wassink, H., Haaker, H., and Hagen, W.R. 1993. Redox properties and EPR spectroscopy of the P clusters of Azotobacter vinelandii MoFe protein. European Journal of Biochemistry 212 51-61. 

Three-iron clusters. Despite the availability of an X-ray crystallographic structure determination of Azotobacter vinelandii ferredoxin I (27), which contains both a normal 4Fe-4S cluster and a 3Fe cluster, the fundamental properties and even the structures... 

Fd I, cyclic voltammetry, 38 130-131 Vfe proteins, 36 90-91 Azotobacter Fd 1, redox properties, 38 HSUS... 

The next important property of PolyP-PHB complexes is their effect on DNA transfer into bacterial cells. It was the striking correlation between PolyP-PHB concentrations and transformation efficiencies in Azotobacter vinelandii, Bacillus subtilis and E. coli that led Reusch and Sadoff (1988) to postulate that the complexes are involved in DNA transmembrane transport. 

According to recent data, the property of dithionite as an electron donor for nitrogenase is different from that of the natural donor flavodoxin (Burgess and Lowe, 1996). Flavodoxin from Azotobacter vinelandii has the redox potential equal to -0.515 V for the reversible transition between the semiquinone and hydroquinone forms of flavodoxin. Unlike dithionite, flavodoxin can reversibly reduce the [Fe4S4]+l cluster Av2 by one electron to the [Fe4S4]° state in which all iron ions exist in the ferrous form. It is assumed that, under natural conditions, two electrons can transfer from Av2 to Avl. Flavodoxin reduces both Av2 bound to Avl and free Av2 in a solution. The apparent rate constants of these reactions are 400 s 1 and > 1000 s"1, respectively (Duyvis et al. 1998). 

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. 

That hydroxylamine might not be an obligatory intermediate, or occur as a free intermediate, in the reduction of nitrite to ammonia is suggested by the properties of nitrite reductases of Azotobacter chroococcum and Escherichia coli. The former is an adaptive enzyme, the formation of which requires nitrate or nitrite in the culture (31,2). It is FAD-depen-dent and presumably contains metals and p-mercuribenzoate inhibitable... 

Spee, J. H., Arendsen, A. F., Wassink, H., Marritt, S. J., Hagen, W. R., and Haaker, H., 1998, Redox properties and elech on paramagnetic resonance spectroscopy of die d ansition state complex of Azotobacter vinelandii nid ogenase FEBS Letters 432 55n58. 

The two nitrogenase proteins, Fe-protein and MoFe-protein, are composed of a total of three different types of subunits and contain three different types of metal centers. The properties of the nitrogenase proteins have been extensively studied and are summarized below. To distinguish the two nitrogenase proteins isolated from different bacterial sources, the MoFe-protein and Fe-protein are designated as components 1 and 2, respectively, preceded by a two-letter abbreviation of the source species and genus i.e., Avl is MoFe-protein isolated from Azotobacter vinelandii and Cp2 is Fe-protein isolated from Clostridium pasteurianum, etc. 

The discovery of Mo-independent nitrogenases is so recent that their contribution to the global cycling of N is unknown. There is good evidence that they are widely distributed in organisms other than in Azotobacter. Recently a nifHDK deletion strain of the photosynthetic bacteria Rhodobacter capsulatus was shown to grow on N2 in medium deficient in Mo and V. Nitrogenase with properties similar to the third... 

One of the most significant discoveries in Fe-S biochemistry in the last decade has been that of [3Fe-4S] clusters. Beinert and Thomson (114) have summarized the early work leading to the recognition of these clusters. This work has culminated in the proof by protein crystallography of the voided-cubane structure 3 (Fig. 1) for clusters in Azotobacter vinelandii (/4v) Fd I (which also contains one [4Fe-4S] cluster) (11, 13, 14), Desul-fovibrio gigas (Dg) Fd II (12, 15), and aconitase from pig heart (115). In these clusters, Fe-Fe separations occur in the range 2.M-2.77 A. As will be seen, aconitase and Dg Fd II assume particular significance in the context of site-specific properties. 

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