Binds the cellulose synthase activator, bis-(3'-5') cyclic diguanylic acid (c-di-GMP). Glycan metabolism; bacterial cellulose biosynthesis. Tightly associated with the cellulose synthase catalytic subunit. The genes bscA, bcsB, bcsZ and bcsC are constitutively transcribed but cellulose synthesis occurs only when DgcC, a putative transmembrane protein regulated by CsgD, is expressed. Cellulose production is abolished in E.coli K12. Belongs to the AcsB/BcsB family.