ACTIVATION OF THE DEPHOSPHORYLATION OF NITROGEN REGULATOR I-PHOSPHATE OF ESCHERICHIA-COLI

The transcription of sigma(54) RNA polymerase-dependent nitrogen-regulated genes is activated by nitrogen regulator I (NR(I))-phosphate. The kinase NR(II) is responsible for the phosphorylation of NR(I). It has been shown that NR(II) also has the ability to dephosphorylate NR(I)-phosphate but only when P-II is present at a concentration greatly in excess of that of NR(II). We have now shown that glutamate enables P-II to stimulate the dephosphorylation of NR(I)-phosphate when present in equimolar concentration with NR(II). This effect of glutamate appears to be a backup control that becomes effective when the normal regulation of P-II activity is disabled.