Evidence for a Second Interaction between the Regulatory Amino-terminal and Central Output Domains of the Response Regulator NtrC (Nitrogen Regulator I) in Escherichia coli

Albert Carson Harrod, Xiaofeng Yang, Matthew Junker, Larry Reitzer

Research output: Contribution to journalArticle

5 Scopus citations


Nitrogen limitation in Escherichia coli activates about 100 genes. Their expression requires the response regulator NtrC (also called nitrogen regulator I or NRI). Phosphorylation of the amino-terminal domain (NTD) of NtrC activates the neighboring central domain and leads to transcriptional activation from promoters that require σ54-containing RNA polymerase. The NTD has five β strands alternating with five α helices. Phosphorylation of aspartate 54 has been shown to reposition α helix 3 to β strand 5 (the "3445 face") within the NTD. To further study the interactions between the amino-terminal and central domains, we isolated strains with alterations in the NTD that were able to grow on a poor nitrogen source in the absence of phosphorylation by the cognate sensor kinase. We identified strains with alterations located in the 3445 face and α helix 5. Both types of alterations stimulated central domain activities. The α helix 5 alterations differed from those in the 3445 face. They did not cause a large scale conformational change in the NTD, which is not necessary for transcriptional activation in these mutants. Yeast two-hybrid analysis indicated that substitutions in both α helix 5 and the 3445 face diminish the interaction between the NTD and the central domain. Our results suggest that α helix 5 of the NTD, in addition to the 3445 face, interacts with the central domain. We present a model of interdomain signal transduction that proposes different functions for α helix 5 and the 3445 face.

Original languageEnglish (US)
Pages (from-to)2350-2359
Number of pages10
JournalJournal of Biological Chemistry
Issue number4
StatePublished - Jan 23 2004


ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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