title: (1,3;1,4)-β-Glucan Biosynthesis by the CSLF6 Enzyme: Position and Flexibility of Catalytic Residues Influence Product Fine Structure.
abstract: Cellulose synthase-like F6 (CslF6) genes encode polysaccharide synthases responsible for (1,3;1,4)-β-glucan biosynthesis in cereal grains. However, it is not clear how both (1,3)- and (1,4)-linkages are incorporated into a single polysaccharide chain and how the frequency and arrangement of the two linkage types that define the fine structure of the polysaccharide are controlled. Through transient expression in Nicotiana benthamiana leaves, two CSLF6 orthologs from different cereal species were shown to mediate the synthesis of (1,3;1,4)-β-glucans with very different fine structures. Chimeric cDNA constructs with interchanged sections of the barley and sorghum CslF6 genes were developed to identify regions of the synthase enzyme responsible for these differences. A single amino acid residue upstream of the TED motif in the catalytic region was shown to dramatically change the fine structure of the polysaccharide produced. The structural basis of this effect can be rationalized by reference to a homology model of the enzyme and appears to be related to the position and flexibility of the TED motif in the active site of the enzyme. The region and amino acid residue identified provide opportunities to manipulate the solubility of (1,3;1,4)-β-glucan in grains and vegetative tissues of the grasses and, in particular, to enhance the solubility of dietary fibers that are beneficial to human health.
authors.affiliation: Australian Research Council Centre of Excellence in Plant Cell Walls, School of Agriculture, Food and Wine, University of Adelaide , Waite Campus, Glen Osmond, South Australia 5064, Australia.
authors.forename: George
authors.initials: G
authors.lastname: Dimitroff
authors.affiliation: Australian Research Council Centre of Excellence in Plant Cell Walls, School of Agriculture, Food and Wine, University of Adelaide , Waite Campus, Glen Osmond, South Australia 5064, Australia.
authors.forename: Alan
authors.initials: A
authors.lastname: Little
authors.affiliation: Australian Research Council Centre of Excellence in Plant Cell Walls, School of Agriculture, Food and Wine, University of Adelaide , Waite Campus, Glen Osmond, South Australia 5064, Australia.
authors.forename: Jelle
authors.initials: J
authors.lastname: Lahnstein
authors.affiliation: Australian Research Council Centre of Excellence in Plant Cell Walls, School of Agriculture, Food and Wine, University of Adelaide , Waite Campus, Glen Osmond, South Australia 5064, Australia.
authors.forename: Julian G
authors.initials: JG
authors.lastname: Schwerdt
authors.affiliation: Division of Glycoscience, School of Biotechnology, Royal Institute of Technology (KTH), AlbaNova University Center , 106 91 Stockhom, Sweden.
authors.forename: Vaibhav
authors.initials: V
authors.lastname: Srivastava
authors.affiliation: Australian Research Council Centre of Excellence in Plant Cell Walls, School of Agriculture, Food and Wine, University of Adelaide , Waite Campus, Glen Osmond, South Australia 5064, Australia.
authors.forename: Vincent
authors.initials: V
authors.lastname: Bulone
authors.affiliation: Australian Research Council Centre of Excellence in Plant Cell Walls, School of Agriculture, Food and Wine, University of Adelaide , Waite Campus, Glen Osmond, South Australia 5064, Australia.
authors.forename: Rachel A
authors.initials: RA
authors.lastname: Burton
authors.affiliation: Australian Research Council Centre of Excellence in Plant Cell Walls, School of Agriculture, Food and Wine, University of Adelaide , Waite Campus, Glen Osmond, South Australia 5064, Australia.
authors.forename: Geoffrey B
authors.initials: GB
authors.lastname: Fincher
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D020134:Catalytic Domain; D019295:Computational Biology; D004043:Dietary Fiber / Q000032:analysis*; D005103:Expert Systems; D005964:Glucosyltransferases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001467:Hordeum / Q000201:enzymology*; D006801:Humans; D007527:Isoenzymes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D008968:Molecular Conformation; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017354:Point Mutation; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D016415:Sequence Alignment; D045868:Sorghum / Q000201:enzymology*; D040681:Structural Homology, Protein; D047071:beta-Glucans / Q000737:chemistry / Q000378:metabolism*
chemical_list: D004043:Dietary Fiber; D007527:Isoenzymes; D010446:Peptide Fragments; D010940:Plant Proteins; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D047071:beta-Glucans; C067858:beta-glucan, (1-3)(1-4)-; D005964:Glucosyltransferases; C478648:cellulose synthase