Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.7.1.2 (nitrate reductase)
 3,861 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The maturation of Escherichia coli nitrate reductase A requires the incorporation of the Mo-(bis-MGD) cofactor to the apoprotein. For this process, the NarJ chaperone is strictly required. We report the first description of protein interactions between molybdenum cofactor biosynthetic proteins (MogA, MoeA, MobA, and MobB) and the aponitrate reductase (NarG) using a bacterial two-hybrid approach. Two conditions have to be satisfied to allow the visualization of the interactions, (i) the presence of an active and mature molybdenum cofactor and (ii) the presence of the NarJ chaperone and of the NarG structural partner subunit, NarH. Formation of tungsten-substituted cofactor prevents the interaction between NarG and the four biosynthetic proteins. Our results suggested that the final stages of molybdenum cofactor biosynthesis occur on a complex made up by MogA, MoeA, MobA, and MobB, which is also in charge with the delivery of the mature cofactor onto the aponitrate reductase A in a NarJ-assisted process.
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PMID:Involvement of the molybdenum cofactor biosynthetic machinery in the maturation of the Escherichia coli nitrate reductase A. 1524 36

Chlorate-resistant Nicotiana plumbaginifolia (cv Viviani) mutants were found to be deficient in the nitrate reductase apoprotein (NR(-)nia). Because they could not grow with nitrate as sole nitrogen source, they were cultivated as graftings on wild-type Nicotiana tabacum plants. The grafts of mutant plants were chlorotic compared to the grafts of wild type. Mutant leaves did not accumulate nitrogen and nitrate but contained less malate and more glutamine than wild leaves. They exhibited a slight increase of the proportion of the light-harvesting chlorophyll a/b protein complexes and a lowering of the efficiency of energy transfer between these complexes and the active centers. After a 3 second (14)CO(2) pulse, the total (14)C incorporation of the mutant leaves was approximately 20% of that of the control. The (14)C was essentially recovered in ribulose bisphosphate in these plants. It was consistent with a decline of ribulose bisphosphate carboxylase activity observed in the mutant. After a 3 second (14)CO(2) pulse followed by a 60 second chase with normal CO(2), (14)C was mainly accumulated in starch which was labeled more in the mutant than in the wild type. These results confirm the observation that in the nitrate reductase deficient leaves, chloroplasts were loaded with large starch inclusions preceding disorganization of the photosynthetic apparatus.
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PMID:Consequence of Absence of Nitrate Reductase Activity on Photosynthesis in Nicotiana plumbaginifolia Plants. 1666 7

A-type carrier (ATC) proteins of the Isc (iron-sulfur cluster) and Suf (sulfur mobilization) iron-sulfur ([Fe-S]) cluster biogenesis pathways are proposed to traffic preformed [Fe-S] clusters to apoprotein targets. In this study, we analyzed the roles of the ATC proteins ErpA, IscA, and SufA in the maturation of the nitrate-inducible, multisubunit anaerobic respiratory enzymes formate dehydrogenase N (Fdh-N) and nitrate reductase (Nar). Mutants lacking SufA had enhanced activities of both enzymes. While both Fdh-N and Nar activities were strongly reduced in an iscA mutant, both enzymes were inactive in an erpA mutant and in a mutant unable to synthesize the [Fe-S] cluster scaffold protein IscU. It could be shown for both Fdh-N and Nar that loss of enzyme activity correlated with absence of the [Fe-S] cluster-containing small subunit. Moreover, a slowly migrating form of the catalytic subunit FdnG of Fdh-N was observed, consistent with impeded twin arginine translocation (TAT)-dependent transport. The highly related Fdh-O enzyme was also inactive in the erpA mutant. Although the Nar enzyme has its catalytic subunit NarG localized in the cytoplasm, it also exhibited aberrant migration in an erpA iscA mutant, suggesting that these modular enzymes lack catalytic integrity due to impaired cofactor biosynthesis. Cross-complementation experiments demonstrated that multicopy IscA could partially compensate for lack of ErpA with respect to Fdh-N activity but not Nar activity. These findings suggest that ErpA and IscA have overlapping roles in assembly of these anaerobic respiratory enzymes but demonstrate that ErpA is essential for the production of active enzymes.
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PMID:A-type carrier protein ErpA is essential for formation of an active formate-nitrate respiratory pathway in Escherichia coli K-12. 2208 93

The activities of nitrite reductase (EC 1.7.7.1) are 60-70% of wild-type activity in pigment-deficient leaves of the chloroplast-ribosomedeficient mutants 'albostrians' (Hordeum vulgare) and 'iojap' (Zea mays). The activity and apoprotein of nitrate reductase (EC 1.6.6.1.) are lacking in the barley mutant. Only very low activities of nitrate reductase can be extracted from leaves of the maize mutant. The molybdenum cofactor of nitrate reductase and xanthine dehydrogenase (EC 1.2.3.2) is present in maize and barley mutant plants. However, it is not inducible by nitrate in pigment-deficient leaves of 'albostrians'. From these results we conclude: (i) Nitrite reductase (a chloroplast enzyme) is synthesized in the cytoplasm and does not need the presence of nitrate reductase for the induction and maintenance if its activity. (ii) The loss or low activity of nitrate reductase is a consequence of the inability of the mutants to accumulate the apoprotein of this enzyme. (iii) The chloroplasts influence the accumulation (i.e. most probably the synthesis) of the nonchloroplast enzyme, nitrate reductase. The accumulation of nitrate reductase needs a chloroplast factor which is not provided by mutant plastids blocked at an early stage of their development.
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PMID:Nitrate reductase is not accumulated in chloroplast-ribosome-deficient mutants of higher plants. 2423 51

Mutant cell lines lacking nitrate reductase activity were analyzed genetically. Protoplasts from one apoprotein defective (nia) and four cofactor defective (cnx) mutants were fused in all possible pairwise combinations with the aid of polyethylene glycol. Complementing hybrids were detected by their ability to grow with nitrate as sole nitrogen source and confirmed by measuring their nitrate reductase activity. Strong complementation was observed in all types of nia+cnx hybrids, whereas the cnx mutants failed to complement each other. From the results it can be concluded that the mutants studied are recessive and that the four cnx mutants are alleles of the same pair of duplicate loci (cnxA1, cnxA2).
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PMID:Complementation analysis of nitrate reductase deficient mutants of Nicotiana tabacum by somatic hybridization. 2426 65

Induction of nitrate reductase (EC 1.6.6.1) activity was measured in Paul's Scarlet rose cell suspensions cultured in media containing nitrate (NO 3 (-) ) or urea (U) as nitrogen source, and with (+Mo) or without molybdenum (-Mo). There was a lag of 30 min during induction by NO 3 (-) in +Mo cultures but no lag occurred during induction after adding Mo to NO 3 (-) -Mo or to U-Mo cultures preincubated with NO 3 (-) . Actinomycin D, cycloheximide, and puromycin completely blocked induction by NO 3 (-) , but had no effect on the initial rate of induction by Mo. Cycloheximide and puromycin blocked induction by NO 3 (-) more quickly than actinomycin D. Induction by NO 3 (-) appeared to involve mRNA-dependent synthesis of apoprotein followed by rapid activation with molybdenum in intact cells independently of protein synthesis. Nitrate-induced apoprotein appeared less stable than the holoenzyme. When induced by NO 3 (-) in the absence of Mo, apoprotein concentration was about half the amount of maximally induced nitrate reductase. Cycloheximide stabilised preformed nitrate reductase which disappeared steadily in the presence of puromycin. Apoprotein was not stabilised by either antimetabolite.
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PMID:Nitrate reductase activity in Paul's scarlet rose suspension cultures and the differential role of nitrate and molybdenum in induction. 2441 75

The cytosolic iron-sulfur cluster assembly (CIA) system assembles iron-sulfur (FeS) cluster cofactors and inserts them into >20 apoprotein targets residing in the cytosol and nucleus. Three CIA proteins, called Cia1, Cia2, and Met18 in yeast, form the targeting complex responsible for apo-target recognition. There is little information about the structure of this complex or its mechanism of CIA substrate recognition. Herein, we exploit affinity co-purification and size exclusion chromatography to determine the subunit connectivity and stoichiometry of the CIA targeting complex. We conclude that Cia2 is the organizing center of the targeting complex, which contains one Met18, two Cia1, and four Cia2 polypeptides. To probe target recognition specificity, we utilize the CIA substrates Leu1 and Rad3 as well as the Escherichia coli FeS-binding transcription factor FNR (fumerate nitrate reductase). We demonstrate that both of the yeast CIA substrates are recognized, whereas the bacterial protein is not. Thus, while the targeting complex exhibits flexible target recognition in vitro, it cannot promiscuously recognize any FeS protein. Additionally, we demonstrate that the full CIA targeting complex is required to stably bind Leu1 in vitro, whereas the Met18-Cia2 subcomplex is sufficient to recognize Rad3. Together, these results allow us to propose a unifying model for the architecture of this highly conserved complex and demonstrate what component or subcomplexes are vital for target identification.
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PMID:Identifying the Protein Interactions of the Cytosolic Iron-Sulfur Cluster Targeting Complex Essential for Its Assembly and Recognition of Apo-Targets. 2853 47


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