8DQK

Intermediate resolution structure of barley (1,3;1,4)-beta-glucan synthase CslF6.

Summary for 8DQK

• Entry DOI: 10.2210/pdb8dqk/pdb
• EMDB information: 27655
• Descriptor: Cellulose synthase-like CslF6 (1 entity in total)
• Functional Keywords: glucan, glycosyltransferase, cellulose, barley, transferase
• Biological source: Hordeum vulgare
• Total number of polymer chains: 1
• Total formula weight: 105193.80

Authors

Ho, R.,Purushotham, P.,Zimmer, J. (deposition date: 2022-07-19, release date: 2022-11-30, Last modification date: 2024-06-12)

Primary citation

Purushotham, P.,Ho, R.,Yu, L.,Fincher, G.B.,Bulone, V.,Zimmer, J.
Mechanism of mixed-linkage glucan biosynthesis by barley cellulose synthase-like CslF6 (1,3;1,4)-beta-glucan synthase.
Sci Adv, 8:eadd1596-eadd1596, 2022

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.

PubMed: 36367939
DOI: 10.1126/sciadv.add1596

Experimental method

ELECTRON MICROSCOPY (4 Å)