Nitrate reductase domains

Fig. 3. Schematic diagram of the Arabidopsis thaliana nitrate reductase domains and the amino acid homology with nitrate reductases from other species and other proteins. Arabidopsis thaliana amino acid sequence is from Crawford et al. (1988). Other sequence data are as follows Nicotiana tabacum, Nia 2, N. sylvestris type (Vaucheret et al., 1989b) Hordeum vu/ ore(K. M. Schnorr, A. Kleinhofs, and R. L. Warner, unpublished data) Oryza sativa (Choi et al., 1989) Aspergillus nidulans (Kinghom and Campbell, 1989) rat liver sulfite oxidase (Rlso) (Crawford et al., 1988) chicken microsomal cytochrome (CM cyt b5) (Ndbrega and Ozols, 1971) cytochrome bf reductase, bovine (Ozols et al., 1985) cytochrome reductase, human (Yubisui et al., 1984).

Thus for dehydrogenase partial activities of NR, the 28kDa FAD domain alone is a NADH ferricyanide reductase (NADH FR) and the FAD domain linked to the haem domain (40kDa) is a NA DH cytochrome c reductase (NADH CR) as well as a NADH dichloro-phenolindophenol reductase (NADH.DR). As for the nitrate-reducing activities, the methylviologen nitrate reductase (MV NR) and the reduced flavin nitrate reductase (FMN NR) activities involve the MoCo domain (75 kDa) linked to the haem domain, whereas reduced brom-... 

Campbell, W.H. Kinghom, J.R. (1990). Functional domains of assimilatory nitrate reductases and nitrite reductases. Trends in Biochemistry 15, 315-19. 

Cannons, A.C., Iida, N. Solomonson, L.P. (1991). Expression of a cDNA clone encoding the haem-binding domain of Chlorella nitrate reductase. Biochemical Journal 278, 203-9. 

Crawford, N.N., Smith, M., Bellissimo, D. Davies, R.W. (1988). Sequence and nitrate regulation of the Arabidopsis thaliana mRNA encoding nitrate reductase, a metalloflavoprotein with three functional domains. Proceedings of the National Academy of Sciences (USA) 85, 5006-10. 

Daniel-Vedele, F., Dorbe, M.F., Caboche, M. Rouze, P. (1989). Cloning and analysis of the tomato nitrate reductase-encoding gene protein domain structure and amino acid homologies in higher plants. Gene 85, 371-80. 

Hyde, G.E. Campbell, W.H. (1990). High-level expression in Escherichia coli of the catalytically active flavin domain of corn leaf NADH-nitrate, reductase and its comparison to human NADH-cytochrome b5 reductase. Biochemical and Biophysical Research Communications 168, 1285-91. 

LS, K.H.D. Lederer, F. (1983). On the presence of a heme-binding domain homologous to cytochrome b5 in Neurospora crassa assimilatory nitrate reductase. The EMBO Journal 2, 1909-14. 

Meyer, C., Levin, J.M., Roussel, J.M. Rouze, P. (1991). Mutational and structural analysis of the nitrate reductase haem domain of Nicotiana plumbaginifolia. Journal of Biological Chemistry 266, 20561-6. 

Solomonson, L.P., Barber, M.J., Robbins, A.P. Oaks, A. (1986). Functional domains of assimilatory NADH nitrate reductase from Chlorella. Journal of Biological Chemistry 261, 11290-4. 

Douglas, P., Moorhead, G., Hong, Y., Morrice, N., and MacKintosh, C., 1998, Purification of a nitrate reductase kinase from Spinaceaa oleracea leaves, and its identification as a calmodulin-domain protein kinase, Planta 206 43511442. 

Lu, G., Lindqvist, Y., Schneider, G., Dwivedi, U., and Campbell, W. H., 1995, Structural studies on com nitrate reductase refined structure of the cytochrome b reductase fragment at 2.5 A, its ADP complex and an active-site mutant and modeling of the cytochrome b domain, J. Mol. Biol. 248 9319948. 

Labeyrie et al. (41) isolated a trypsin fragment of 11 kDa from S. cerevisiae flavocytochrome 62 that contained heme but was devoid of flavin and had no lactate dehydrogenase activity. The fragment, which was referred to as cytochrome 62 core, was found to have spectral properties very like those of microsomal cytochrome 65 (41). This similarity with cytochrome 65 is borne out by comparisons of amino acid sequence (42-44). The sequence similarity extends to related heme domains of sulfite oxidase (45, 46) and assimilatory nitrate reductase (47). The existence of a protein family with a common cytochrome 65 fold was suggested by Guiard and Lederer (48) and this is supported by the close similarity between the three-dimensional structures of microsomal cytochrome 65 (49) and the cytochrome domain of flavocytochrome 62 (23-25). 

The two-domain, structural motif in FNR represents a common structural feature in a large class of enzymes that catalyze electron transfer between a nicotinamide dinucleotide molecule and a one-electron carrier. Beside the photosynthetic electron-transfer enzyme, others non-photosynthetic ones include flavodoxin reductase, sulfite reductase, nitrate reductase, cytochrome reductase, and NADPH-cyto-chrome P450 reductase. FNR belongs to the group of so-called dehydrogenases-electron transferases, i.e., flavoproteins that catalyze electron transfer from two, one-electron donor molecules to a single two-electron acceptor molecule. 

To date, only the role of vanadium in biogenic nitrogen fixation has been established unambiguously. In addition, there are a few reports on a putative importance of vanadium in (bacterial) nitrate reductases, otherwise a domain of molybdenum. These reports are based on investigations which remain to be backed up. They are nonetheless briefly addressed, with a question mark, in Section 4.4.2. 

Enzymes that belong to the sulfite oxidase family are comprised of the assim-ilatory eukaryotic nitrate reductases, bacterial YedY and the sulfite oxidizing enzymes. The latter are found in bacteria, plants, animals and humans, and are the primary focus of this section. A similar protein fold of the Mo domain, the so-called SUOX fold, characterizes these enzymes. The nature of the protein fold is one key factor that distinguishes SO family enzymes from the MOSC family proteins, which possess a very similar... 

Fig. 1. Structure-function model of Chlorella assimilatoiy NADH-nitrate reductase. Features of the model include four identical subunits with two diiferent binding domains and the FAD/ NADH and heme/molybdenum domains connected by a protease-sensitive hinge region. Solid arrows indicate physiological electron transfer reactions, and dashed arrows indicate electron transfer to or from artificial acceptors or donors (partial reactions). [Reproduced with permission from Solomonson et al. (1986).]...

Fig. 2. Structure-function model of spinach assimilatory NADH nitrate reductase. Native enzyme consists of two subunits, each comprising three separate domains Mo, molybdenum domain, 75 kDa Cyt-b, cytochrome bi domain, 14 kDa and FAD, FAD domain, 28 kDa, connected by the protease-sensitive hinge regions. [Reproduced with permission from Kubo et al. (1988).]...

Some metalloflavoproteins contain heme groups. The previously mentioned flavocytochrome b2 of yeast is a 230-kDa tetramer, one domain of which carries riboflavin phosphate and another heme. A flavocytochrome from the photosynthetic sulfur bacterium Chromatium (cytochrome c-552)279 is a complex of a 21-kDa cytochrome c and a 46-kDa flavoprotein containing 8a-(S-cysteinyl)-FAD. The 670-kDa sulfite reductase of E. coli has an a8P4 subunit structure. The eight a chains bind four molecules of FAD and four of riboflavin phosphate, while the P chains bind three or four molecules of siroheme (Fig. 16-6) and also contain Fe4S4 clusters.280 281 Many nitrate and some nitrite reductases are flavoproteins which also contain Mo or... 

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