abstract:NtrC (Nitrogen regulatory protein C) is the name of the protein necessary for the prokaryotic regulation transcription factor sigma N (sigma 54) to form an open complex with RNA polymerase in order to activate glnA transcription. The open -> closed conformational change of the sigma N-RNA polymerase complex around the glutamine synthetase gene promoter requires ATP and involves the formation of a loop between the enhancer and the promoter regions.