May act 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 (Potential). Binds bis-(3'-5') cyclic diguanylic acid (c-di-GMP) with a dissociation constant of 170 nM in the presence of 10 mM KCl and with 100 nM in its absence. Binds 1 to 2 c-di-GMP per subunit. Only 1 c-di-GMP is seen in the wild-type crystal, while 2 are seen in the mutant. Depending on the concentration of K(+) stoichiometries of 1:1, 1.43:1 and 2:1 are determined by isothermal titration calorimetry. Dimer. Belongs to the YcgR family.