Isolation of the nitrogen assimilation regulator NRI, the product of the glnG gene of Escherichia coli

AUTOR(ES)

Reitzer, Lawrence J.

RESUMO

The product of the glnG gene, a member of the complex glnALG operon, is an essential component in the response of Escherichia coli K-12 and other enteric bacteria to nitrogen-limited growth. We have purified this protein which we propose to call “NRI,” for nitrogen regulator I, to about 95% purity from an overproducing strain. Purified NRI was identified as a dimer by gel filtration. NRI specifically inhibited initiation of transcription from a DNA fragment containing the glnL promoter but was without effect on lacZ transcription. We determined the intracellular concentration of NRI under different growth conditions by using immunological techniques. The ratio of glutamine synthetase polypeptides, the product of the glnA gene, to NRI polypeptides was about 80:1. NRI was not rapidly degraded after ammonia shock, even though the ability to activate nitrogen-controlled systems was lost.

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