Activation of transcription of hut DNA by glutamine synthetase

The correct transcription of the hut (histidine utilization) operon DNA of Salmonella typhimurium requires activation either by 3':5'-cyclic adenosine monophosphate and catabolite-activating protein or by nonadenylylated glutamine synthetase (EC 6.3.1.2.). Thus, glutamine synthetase plays a regulatory role distinct from its enzymatic function.