PMID:9495755
| Citation |
Muse, WB and Bender, RA (1998) The nac (nitrogen assimilation control) gene from Escherichia coli. J. Bacteriol. 180:1166-73 |
|---|---|
| Abstract |
The nitrogen assimilation control gene, nac, was detected in Escherichia coli but not in Salmonella typhimurium by Southern blotting, using a probe from the Klebsiella aerogenes nac (nacK) gene. The E. coli nac gene (nacE) was isolated from a cosmid clone by complementation of a nac mutation in K. aerogenes. nacE was fully functional in this complementation assay. DNA sequence analysis showed considerable divergence between nacE and nacK, with a predicted amino acid sequence identity of only 79% and most of the divergence in the C-terminal half of the protein sequence. The total predicted size of NAC(E) is 305 amino acids, the same as for NAC(K). A null mutation, nac-28, was generated by reverse genetics. Mutants bearing nac-28 have a variety of phenotypes related to nitrogen metabolism, including slower growth on cytosine, faster growth on arginine, and suppression of the failure of an Ntr-constitutive mutant to grow with serine as sole nitrogen source. In addition to a loss of nitrogen regulation of histidase formation, nac-28 mutants also showed a loss of a weak repression of glutamate dehydrogenase formation. This repression was unexpected because it is balanced by a NAC-independent activation of glutamate dehydrogenase formation during nitrogen-limited growth. Attempts to purify NAC(E) by using methods established for NAC(K) failed, and NAC(E) appears to be degraded with a half-life at 30 degrees C as short as 15 min during inhibition of protein synthesis. |
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| Keywords |
Arginine/metabolism; Bacterial Proteins/genetics; Bacterial Proteins/metabolism; Base Sequence; Cosmids; Cytosine/metabolism; DNA-Binding Proteins/genetics; DNA-Binding Proteins/metabolism; Escherichia coli/genetics; Escherichia coli/growth & development; Escherichia coli/metabolism; Escherichia coli Proteins; Gene Expression Regulation, Bacterial; Genes; Genes, Bacterial; Genetic Complementation Test; Glutamate Dehydrogenase/biosynthesis; Glutamate Dehydrogenase/genetics; Histidine Ammonia-Lyase/biosynthesis; Histidine Ammonia-Lyase/genetics; Klebsiella pneumoniae/genetics; Molecular Sequence Data; Mutation; Nitrogen/metabolism; Promoter Regions, Genetic; Salmonella typhimurium/genetics; Transcription Factors/genetics; Transcription Factors/metabolism |
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