Acts as a flagellar brake, regulating swimming and swarming in a bis-(3'-5') cyclic diguanylic acid (c-di-GMP)-dependent manner. Increasing levels of c-di-GMP lead to decreased motility (By similarity). Binds c-di-GMP with a dissociation constant of 165 nM. Binds 2 intercalated (c-di-GMP) dimers per subunit. Interacts with the flagellar basal bodies (By similarity). Monomer. Binding of c-di-GMP produces a dimer to monomer transition. Belongs to the YcgR family.