Azotobacter vinelandii structure

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

Fig. 2. The structure of the Fe protein (Av2) from Azotobacter vinelandii, after Geor-giadis et al. (1). The dimeric polypeptide is depicted by a ribbon diagram and the Fe4S4 cluster and ADP by space-filling models (MOLSCRIPT (196)). The Fe4S4 cluster is at the top of the molecule, bound equally to the two identical subunits, Emd the ADP molecule spans the interface between the subunits with MoO apparently binding in place of the terminal phosphate of ATP.

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.

A relationship between the redox state of an iron—sulfur center and the conformation of the host protein was furthermore established in an X-ray crystal study on center P in Azotobacter vinelandii nitroge-nase (270). In this enzyme, the two-electron oxidation of center P was found to be accompanied by a significant displacement of about 1 A of two iron atoms. In both cases, this displacement was associated with an additional ligation provided by a serine residue and the amide nitrogen of a cysteine residue, respectively. Since these two residues are protonable, it has been suggested that this structural change might help to synchronize the transfer of electrons and protons to the Fe-Mo cofactor of the enzyme (270). 

Lawson, D. M., Williams, C. E., Mitchenall, L. A., and Pau, R. N. (1998). Ligand size is a major determinant of specificity in periplasmic oxyanion-binding proteins the 1.2 A resolution crystal structure of Azotobacter vinelandii ModA. Structure 6, 1529-1539. 

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...

The last class of iron-sulfur proteins to be considered is that of the bacterial 7Fe ferredoxins, which contain both an Fe3S4 and an Fe4S4 cluster. Figure 28 shows the molecular structure of that from Azotobacter vinelandii (FW — 12 700).53... 

In confirmation of the chemical and electrochemical reversibility of these processes, the one-electron reduced complex of the 7Fe ferredoxin of Azotobacter vinelandii has been structurally characterized. The Fe3S4 cluster, on which the first reduction is centred, maintains a quasi-cuboidal geometry essentially unaltered with respect to the oxidized form some minor structural variation is observed on the peripheral amino acids.55... 

From Azotobacter vinelandii the structures of two siderophores were elucidated. They contain the chromophore Chrd (Fig. 1) and Hse units azotobactin 87-1 (8) (from the three Hse in this sequence two are l and one d configured) from the strain ATCC 12837 314), and azotobactin D (9) (76) from the strain CCM 289. 

Demange P, Bateman A, Dell A, Abdallah MA (1988) Structure of Azotobactin D, a Siderophore of Azotobacter vinelandii Strain D (CCM 289). Biochemistry 27 2745... 

Fukasawa K, Goto M, Sasaki K, Hirata Y, Sato S (1972) Structure of the Yellow-Green Fluorescent Peptide Produced by Iron-deficient Azotobacter vinelandii Strain O. Tetrahedron 28 5359... 

Page WJ, Collinson SK, Demange P, Dell A, Abdallah MA (1991) Azotobacter vinelandii Strains of Disparate Origin Produce Azotobactin Siderophores with Identical Structures. Biol Metals 4 217... 

Schaffher EM, Hartmann R, Taraz K, Budzikiewicz H (1996) Structure Elucidation of Azotobactin 87, Isolated from Azotobacter vinelandii ATCC 12837. Z Naturforsch 51c 139... 

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... 

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. 

Two unusual glycosyl esters of cytidine 5 -pyrophosphate were found in extracts of Azotobacter vinelandii,62 The branched-chain, O-methylated heptose called vinelose was identified as the glycosyl component, and the structures 13 and 14 were assigned to these... 

Youssef NN, Hammond D (1971) The fine structure of the developmental stages of the microsporidian Nosema apis Zander. Tissue Cell 3 283-294 Yu Y, Samuelson J (1994) Primary structure of an Entamoeba histolytica nicotinamide nucleotide transhydrogenase. Mol Biochem Parasitol 68 323-328 Zheng L, Cash VL, Hint DH, Dean DR (1998) Assembly of iron-sulfur clusters. Identification of an iscSUA-hscBA-fdx gene cluster from Azotobacter vinelandii. J Biol Chem 273 13264-13272... 

Formation of L-guluronic acid, a component of the alginic acid-like polysaccharide produced by P. aeruginosa and Azotobacter vinelandii, requires special comment. In this case, a polymer built from /3-(l- 4)-linked D-mannosyluronic acid residues serves as an intermediate in the biosynthesis.204,205 Part of the D-mannosyluronic acid residues in the polymer is subjected to an epimerization at C-5 catalyzed by an exocellular enzyme of the micro-organism,205-207 producing a polysaccharide composed of structural blocks that contain only D-mannosyluronic acid or only l-gulosyluronic acid residues, as well %s some having both. The mechanism of the epimerization remains unclear. 

Some detailed comparisons of the protein environments around the HiPIP and Fd clusters have been made.769,770 It is noteworthy that the HiPIP cluster is more deeply buried (about 4.5 A) than is the case for the clusters in the other iron-sulfur proteins. All iron-sulfur proteins for which structural data are available, with the exception of the three-iron protein from Azotobacter vinelandii, have hydrogen bonding between the cysteine sulfur in the iron-sulfur cluster and the backbone peptide link. It appears that there is an approximate correlation between the number of NH S hydrogen bonds in the environment of a cluster and its redox potential. In HiPIP, these hydrogen bonds become more linear and shorten on reduction of the cluster. It is possible, therefore, that the oxidation states of the cluster may be controlled by the geometries of the hydrogen bonds.770... 

Figure 31 Possible structures for the three-iron proteins (a), the the 3Fe-3S cluster in Azotobacter vinelandii Fdl (b) and (c), the 3Fe-4S cluster in Desutfovibrio gigas Fdll...

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... 

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