This enzyme has three activities: DNA binding, nicotinamide mononucleotide (NMN) adenylyltransferase and ribosylnicotinamide (RN) kinase. The DNA-binding domain binds to the nadB operator sequence in an NAD- and ATP-dependent manner. As NAD levels increase within the cell, the affinity of NadR for the nadB operator regions of nadA, nadB, and pncB increases, repressing the transcription of these genes. The RN kinase activity catalyzes the phosphorylation of RN to form nicotinamide ribonucleotide. The NMN adenylyltransferase activity catalyzes the transfer of the AMP moiety of ATP to nicotinamide ribonucleotide to form NAD(+). The NMN adenylyltransferase domain also functions as the NAD and ATP sensor (By similarity). ATP + beta-nicotinamide D-ribonucleotide + H(+) = diphosphate + NAD(+) ATP + beta-nicotinamide D-riboside = ADP + beta-nicotinamide D-ribonucleotide + H(+) Cofactor biosynthesis; NAD(+) biosynthesis [regulation]. Cofactor biosynthesis; NAD(+) biosynthesis; NAD(+) from nicotinamide D-ribonucleotide: step 1/1.