c-di-GMP-binding protein, a new factor regulating cellulose synthesis in Acetobacter xylinum

A protein which specifically binds cyclic diguanylic acid (c-di-GMP), the reversible allosteric activator of the membrane-bound cellulose synthase system of Acetobacter xylinum, has been identified in membrane preparations of this organism. c-di-GMP binding is of high affinity (KD 20 nM), saturable and reversible. The equilibrium of the reaction is markedly and specifically shifted towards the binding direction by K+. The c-di-GMP binding protein, structurally associated with the cellulose synthase, appears to play a major role in modulating the intracellular concentration of free c-di-GMP and thus may constitute an essential factor in regulating cellulose synthesis in vivo.