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. Copyright (C) 1998 Federation of European Microbiological Societies.
Camarena, L., Poggio, S., García, N., & Osorio, A. (1998). Transcriptional repression of gdhA in Escherichia coli is mediated by the Nac protein. FEMS Microbiology Letters, 167(1), 51–56. https://doi.org/10.1016/S0378-1097(98)00366-8