PMID:3053688

Citation	Sodergren, EJ, Hsu, PY and DeMoss, JA (1988) Roles of the narJ and narI gene products in the expression of nitrate reductase in Escherichia coli. J. Biol. Chem. 263:16156-62
Abstract	Nitrate reductase, released and purified from membrane fractions of Escherichia coli, is composed of three subunits. Formation of the enzyme depends on induction of the nar operon, narGHJI, which is composed of four open reading frames (ORF). Previous studies established that the first two genes in the operon narG and narH encode the alpha and beta subunits, respectively, while formation of the gamma subunit, cytochrome bNR, depends on expression of the promoter distal genes. The narJ and narI genes were subcloned separately into plasmids where each was under the control of the nar promoter. Expression of these plasmids in a mutant which forms only alpha and beta subunits revealed that expression of the narI gene is sufficient to restore normal levels of cytochrome bNR, but expression of both genes is required for assembly of fully active, membrane-bound nitrate reductase. The amino acid composition, the N-terminal sequence, and the sequence of cyanogen bromide fragments derived from the isolated gamma subunit corresponds to that expected for a protein produced by the narI ORF. A protein corresponding to the narJ ORF did not appear to be associated with the purified nitrate reductase complex or with the complex immunoprecipitated from Triton X-100-solubilized membrane preparations. We conclude that narI encodes the gamma subunit (cytochrome bNR) and that while the product of the narJ gene is required for assembly of fully active membrane-bound enzyme it is not tightly associated with the active enzyme.
Links	PubMed
Keywords	Amino Acid Sequence; Cloning, Molecular; Escherichia coli/enzymology; Escherichia coli/genetics; Genes; Genes, Bacterial; Genetic Complementation Test; Macromolecular Substances; Molecular Sequence Data; Mutation; Nitrate Reductases/genetics; Operon; Plasmids; Restriction Mapping; Transcription, Genetic
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
ECOLI:NARI		GO:0009325: nitrate reductase complex	ECO:0000314:		C		Figure 4. Column 2 (0 min); Column 3 (2min) Column 4 (10min). As length of purification process increases, expression decreases - less expression in each consecutive column after column 2. Evidence that narJ is lost during lengthy purification process.	complete CACAO 2300
ECOLI:NARI	part_of	GO:0009325: nitrate reductase complex	ECO:0000314: direct assay evidence used in manual assertion		C		Seeded From UniProt	complete

References

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