Atomic-resolution structure of the cellulose synthase regulator cyclic diguanylic acid.

Cyclic diguanylic acid acts as a regulator for cellulose synthase activity in the bacterium Acetobacter xylinum. We report the x-ray crystal structure of the regulator at atomic resolution. The structure contains two independent molecules that adopt almost identical conformations. The two molecules form self-intercalated units that are stacked on each other. Two different G.G base-pairing modes occur between the stacks. The more stable one has two or possibly three hydrogen bonds between two guanines and is related to the type of hydrogen bonding that is believed to exist between G-rich strands at the ends of chromosomes.