Architecture of a catalytically active homotrimeric plant cellulose synthase complex

Plant cell wall construction crew Plants produce a complex cell wall in which cellulose, a glucose polymer, is a major component. Cellulose fibers are formed from close-packed single chains of cellulose that have been proposed to be formed by multimeric complexes (18 or more subunits) of the enzyme cellulose synthase, which exists in several isoforms. Purushothamet al. determined a cryo–electron microscopy structure of a trimer of a single isoform of cellulose synthase. A large channel forms a path for cellulose chains through the membrane-embedded complex. The structure also reveals oligomeric interfaces and provides a framework for modeling the larger complexes seen in plant membranes. The close arrangement of exit sites for nascent glycan chains is consistent with the enzyme complex playing a role in directing cellulose microfibril formation.Science , this issue p.1089