Member of the two-component regulatory system FlgR/FlgS that induces the transcriptional induction of the genes needed in motility and flagellar biogenesis (PubMed:15231786, PubMed:9882675). Upon phosphorylation by FlgS, functions as a transcriptional regulator and activates transcription of RpoN-dependent flagellar genes (PubMed:10735847, PubMed:15231786). Phosphorylated by FlgS. Disruption leads to loss of motility due to the failure of the mutant strain to express the RpoN-dependent flagellar genes.