title: Isolation of a cDNA encoding a granule-bound 152-kilodalton starch-branching enzyme in wheat.
abstract: Screening of a wheat (Triticum aestivum) cDNA library for starch-branching enzyme I (SBEI) genes combined with 5'-rapid amplification of cDNA ends resulted in isolation of a 4,563-bp composite cDNA, Sbe1c. Based on sequence alignment to characterized SBEI cDNA clones isolated from plants, the SBEIc predicted from the cDNA sequence was produced with a transit peptide directing the polypeptide into plastids. Furthermore, the predicted mature form of SBEIc was much larger (152 kD) than previously characterized plant SBEI (80-100 kD) and contained a partial duplication of SBEI sequences. The first SBEI domain showed high amino acid similarity to a 74-kD wheat SBEI-like protein that is inactive as a branching enzyme when expressed in Escherichia coli. The second SBEI domain on SBEIc was identical in sequence to a functional 87-kD SBEI produced in the wheat endosperm. Immunoblot analysis of proteins produced in developing wheat kernels demonstrated that the 152-kD SBEIc was, in contrast to the 87- to 88-kD SBEI, preferentially associated with the starch granules. Proteins similar in size and recognized by wheat SBEI antibodies were also present in Triticum monococcum, Triticum tauschii, and Triticum turgidum subsp. durum.
authors.affiliation: Plant Biotechnology Institute, National Research Council of Canada, 110 Gymnasium Place, Saskatoon, Saskatchewan, Canada S7N 0W9.
authors.forename: M
authors.initials: M
authors.lastname: Båga
authors.forename: R B
authors.initials: RB
authors.lastname: Nair
authors.forename: A
authors.initials: A
authors.lastname: Repellin
authors.forename: G J
authors.initials: GJ
authors.lastname: Scoles
authors.forename: R N
authors.initials: RN
authors.lastname: Chibbar
mesh_terms: D015061:1,4-alpha-Glucan Branching Enzyme / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D000595:Amino Acid Sequence; D001483:Base Sequence; D015152:Blotting, Northern; D003594:Cytoplasmic Granules / Q000201:enzymology*; D018076:DNA, Complementary / Q000235:genetics / Q000302:isolation & purification; D004792:Enzyme Precursors / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology; D015151:Immunoblotting; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010940:Plant Proteins / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D017434:Protein Structure, Tertiary; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012639:Seeds / Q000201:enzymology / Q000235:genetics; D014908:Triticum / Q000201:enzymology / Q000235:genetics*
chemical_list: D018076:DNA, Complementary; D004792:Enzyme Precursors; D010940:Plant Proteins; D015061:1,4-alpha-Glucan Branching Enzyme