Structural highlights
FunctionPublication Abstract from PubMedMixed-linkage (1,3;1,4)-beta-glucans, which are widely distributed in cell walls of the grasses, are linear glucose polymers containing predominantly (1,4)-beta-linked glucosyl units interspersed with single (1,3)-beta-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)-beta-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)-beta-linkage. Mechanism 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 GB, Bulone V, Zimmer J Sci Adv. 2022 Nov 11;8(45):eadd1596. doi: 10.1126/sciadv.add1596. Epub 2022 Nov , 11. PMID:36367939[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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