Download MendeleyMechanism of mixed-linkage glucan biosynthesis by barley cellulose synthase-like CslF6 (1,3;1,4)-beta-glucan synthase.
Purushotham, P., Ho, R., Yu, L., Fincher, G.B., Bulone, V., Zimmer, J.(2022) Sci Adv 8: eadd1596-eadd1596
- PubMed: 36367939
- DOI: https://doi.org/10.1126/sciadv.add1596
- Primary Citation of Related Structures:
8DQK - PubMed Abstract:
Mixed-linkage (1,3;1,4)-β-glucans, which are widely distributed in cell walls of the grasses, are linear glucose polymers containing predominantly (1,4)-β-linked glucosyl units interspersed with single (1,3)-β-linked glucosyl units. Their distribution in cereal grains and unique structures are important determinants of dietary fibers that are beneficial to human health. We demonstrate that the barley cellulose synthase-like CslF6 enzyme is sufficient to synthesize a high-molecular weight (1,3;1,4)-β-glucan in vitro. Biochemical and cryo-electron microscopy analyses suggest that CslF6 functions as a monomer. A conserved "switch motif" at the entrance of the enzyme's transmembrane channel is critical to generate (1,3)-linkages. There, a single-point mutation markedly reduces (1,3)-linkage formation, resulting in the synthesis of cellulosic polysaccharides. Our results suggest that CslF6 monitors the orientation of the nascent polysaccharide's second or third glucosyl unit. Register-dependent interactions with these glucosyl residues reposition the polymer's terminal glucosyl unit to form either a (1,3)- or (1,4)-β-linkage.
Organizational Affiliation:
Howard Hughes Medical Institute, University of Virginia School of Medicine, Charlottesville, VA 22908, USA.
