Studies with the glnA promoter of S. typhimurium have shown that NtrC bound at the enhancer , located between 2140 , interacts directly with s54 holoenzyme by means of DNA loop formation .
Studies with the glnA promoter of S. typhimurium have shown that NtrC bound at the enhancer , located between 2108 , interacts directly with s54 holoenzyme by means of DNA loop formation .
NtrC-dependent transcription of target genes ( Table 1 ) allows the cell to assimilate low levels of ammonia and utilize alternative nitrogen sources in nutrient-limited environments ; NtrC-regulated glnA ( glutamine synthetase ) and glnHQ ( glutamine transport ) together contribute to S. Typhimurium virulence in a mouse model and increased survival in macrophages ( Klose and Mekalanos , 1997 ) .