, ▁designated ▁N RI - P . ▁Ph osph ory lation ▁of ▁N RI ▁is ▁catal yz ed ▁by ▁NR II , ▁a ▁protein ▁kin ase . ▁If ▁NR II ▁is ▁complex ed ▁with ▁P II A ▁then ▁it ▁will ▁function ▁as ▁a ▁ph osph at ase ▁and ▁N RI - P ▁is ▁converted ▁back ▁to ▁N RI . ▁In ▁this ▁case , ▁trans cription ▁of ▁g ln A ▁ce ases . ▁ ▁G S ▁is ▁subject ▁to ▁completely ▁different ▁regul atory ▁mechan isms ▁in ▁cy an ob acter ia . ▁Instead ▁of ▁the ▁common ▁N tr C - N tr B ▁two ▁component ▁system , ▁cy an ob acter ia ▁har bour ▁the ▁trans cription al ▁reg ulator ▁N tc A ▁which ▁is ▁restricted ▁to ▁this ▁cla de ▁and ▁controls ▁expression ▁of ▁G S ▁and ▁a ▁mult itude ▁of ▁gen es ▁involved ▁in ▁N it ro gen ▁met abol ism . ▁Moreover , ▁G S ▁in ▁Cy an ob acter ia ▁is ▁not ▁c oval ently ▁modified ▁to ▁raise ▁sens itivity ▁for ▁feedback ▁in hib ition . ▁Instead , ▁G S ▁in ▁Cy an ob acter ia ▁is ▁in hib ited ▁by ▁small ▁prote ins , ▁term ed ▁G S ▁in activ ating ▁factors ▁( IF s ) ▁whose ▁trans cription ▁is ▁neg atively ▁reg ulated ▁by ▁N tc A . ▁These ▁in activ ating ▁factors ▁are ▁further more ▁reg ulated ▁by ▁different ▁Non - c oding ▁R N As : ▁The ▁s R NA ▁N si R 4 ▁interact s ▁with