Cellulose synthase catalyzes the beta-1,4 polymerization of glucose residues in the formation of cellulose. In bacteria, the substrate is UDP-glucose. The synthase consists of two subunits (or domains in the frequent cases where it is encoded as a single polypeptide), the catalytic domain modelled here and the regulatory domain (pfam03170). The regulatory domain binds the allosteric activator cyclic di-GMP. The protein is membrane-associated and probably assembles into multimers such that the individual cellulose strands can self-assemble into multi-strand fibrils.