AAA+ ATPase enhancer-binding protein that acts as a transcription regulator and plays a role in the modulation of mucin adhesion and flagellar gene expression (PubMed:9287015, PubMed:11673434, PubMed:26362077). In addition to flagella genes, regulates also expression of biofilm-related genes (PubMed:22581773). Functions as a transcriptional repressor in the absence of c-di-GMP and as an activator when c-di-GMP is present (PubMed:22581773). C-di-GMP interaction leads to active site obstruction, hexameric ring destabilization thus relieving DNA bending and activating gene transcription. Forms homodimers (PubMed:26362077). Forms homohexamers that inhibit transcription initiation (PubMed:26712005). Interacts with FleN; this complex is formed in the presence as well as in the absence of c-di-GMP or ATP (PubMed:22581773). The N-terminal FleQ domain mediates dimerization and is essential for function. Deletion results in the concomitant loss of motility, mucin adhesion, and the ability to synthesize flagellin.