Abstract
In this work we show that the nac gene from Escherichia coli is transcriptionally active, and that its expression is dependent on NRI (NtrC) and sigma-54. Northern blot experiments show a monocistronic nac-specific mRNA that is detected when wild-type cells are grown in nitrogen-limiting conditions. Our data also show that in nitrogen-limiting conditions Nac is involved in the transcriptional repression of the gdhA gene (encoding glutamate dehydrogenase) except when L-glutamine is used as the only nitrogen source. Moreover, the high level of GDH activity observed in a nac mutant strain is reduced when a wild-type nac gene is introduced under control of the lac promoter in N-limiting conditions, but not in L-glutamine or N-excess. These results suggest the existence of an additional mechanism responsible for overcoming repression by Nac.
MeSH terms
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Bacterial Proteins / genetics*
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Bacterial Proteins / metabolism
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DNA-Binding Proteins / genetics*
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DNA-Binding Proteins / metabolism
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Escherichia coli / genetics*
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Escherichia coli / metabolism*
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Escherichia coli Proteins*
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Gene Expression Regulation, Bacterial
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Genes, Bacterial*
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Glutamate Dehydrogenase / genetics*
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Klebsiella pneumoniae / genetics
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Klebsiella pneumoniae / metabolism
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Mutation
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RNA, Bacterial / genetics
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RNA, Bacterial / metabolism
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RNA, Messenger / genetics
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RNA, Messenger / metabolism
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Repressor Proteins / genetics
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Repressor Proteins / metabolism
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Transcription Factors / genetics*
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Transcription Factors / metabolism
Substances
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Bacterial Proteins
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DNA-Binding Proteins
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Escherichia coli Proteins
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NAC protein, bacteria
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Nac protein, E coli
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RNA, Bacterial
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RNA, Messenger
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Repressor Proteins
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Transcription Factors
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Glutamate Dehydrogenase