title: Identification of a novel beta-turn-rich repeat motif in the D hordeins of barley.
abstract: The amino acid sequence of the C-terminal part of a barley D hordein seed protein was deduced from the nucleotide sequence of a partial cDNA. It showed high homology with the HMW glutenin subunits of wheat, both proteins consisting predominately of repeated sequences. Whereas the wheat repeats are based on tri-, hexa- and nonapeptides that are rich in glycine, proline and glutamine, the D hordein also contains eleven copies of a novel unrelated motif: Thr-Thr-Val-Ser. The repeated sequences in the wheat glutenin subunits have been demonstrated to form an unusual spiral supersecondary structure based on beta-turns. Conformational analysis of the Thr-Thr-Val-Ser motif by secondary structure prediction and by circular dichroism spectroscopy of an 18 residue synthetic peptide demonstrates that it also forms beta-turns. Thus, D hordein may also have a spiral structure like that of HMW glutenin, despite the presence of a different repeat motif. This conservation of protein conformation in D hordein and the wheat glutenin subunits may indicate a structural role, perhaps in packing of the proteins within the protein bodies of the developing grain.
authors.affiliation: Department of Agricultural Sciences, University of Bristol, UK.
authors.forename: N G
authors.initials: NG
authors.lastname: Halford
authors.forename: A S
authors.initials: AS
authors.lastname: Tatham
authors.forename: E
authors.initials: E
authors.lastname: Sui
authors.forename: L
authors.initials: L
authors.lastname: Daroda
authors.forename: T
authors.initials: T
authors.lastname: Dreyer
authors.forename: P R
authors.initials: PR
authors.lastname: Shewry
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D002942:Circular Dichroism; D005983:Glutens; D001467:Hordeum / Q000235:genetics*; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000302:isolation & purification; D011487:Protein Conformation; D012091:Repetitive Sequences, Nucleic Acid
chemical_list: D010940:Plant Proteins; D005983:Glutens