Under conditions of nitrogen limitation, the RcNtrB protein phosphorylates RcNtrC. Phosphorylated RcNtrC binds to tandem sites located approximately 100 bases upstream from the promoters that it activates (e.g. the nifA1, nifA2, glnB, anfA, or mopA promoters) and interacts with the sigma70 RNA polymerase to activate transcription. The RcNtrC protein must bind ATP in order to activate transcription; however, ATP hydrolysis is not required for the activation process.