Purification, cloning, and functional expression of sucrose:fructan 6-fructosyltransferase, a key enzyme of fructan synthesis in barley.
Fructans play an important role in assimilate partitioning and possibly in stress tolerance in many plant families. Sucrose:fructan 6-fructosyltransferase (6-SFT), an enzyme catalyzing the formation and extension of beta-2,6-linked fructans typical of grasses, was purified from barley (Hordeum vulgare L.). It occurred in two closely similar isoforms with indistinguishable catalytic properties, both consisting of two subunits with apparent masses of 49 and 23 kDa. Oligonucleotides, designed according to the sequences of tryptic peptides from the large subunit, were used to amplify corresponding sequences from barley cDNA. The main fragment generated was cloned and used to screen a barley cDNA expression library. The longest cDNA obtained was transiently expressed in Nicotiana plumbaginifolia protoplasts and shown to encode a functional 6-SFT. The deduced amino acid sequence of the cDNA comprises both subunits of 6-SFT. It has high similarity to plant invertases and other beta-fructosyl hydrolases but only little to bacterial fructosyltransferases catalyzing the same type of reaction as 6-SFT.
Department of Botany, University of Basel, Switzerland.
N
N
Sprenger
K
K
Bortlik
A
A
Brandt
T
T
Boller
A
A
Wiemken
D000595:Amino Acid Sequence; D002240:Carbohydrate Sequence; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D004790:Enzyme Induction; D005630:Fructans / Q000096:biosynthesis*; D018506:Gene Expression Regulation, Plant; D006026:Glycoside Hydrolases / Q000235:genetics; D006602:Hexosyltransferases / Q000096:biosynthesis / Q000235:genetics* / Q000302:isolation & purification; D001467:Hordeum / Q000201:enzymology / Q000235:genetics*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010446:Peptide Fragments / Q000737:chemistry; D018515:Plant Leaves / Q000201:enzymology / Q000378:metabolism; D010947:Plants, Toxic; D011487:Protein Conformation; D011523:Protoplasts; D011994:Recombinant Proteins / Q000096:biosynthesis; D017421:Sequence Analysis; D017386:Sequence Homology, Amino Acid; D014026:Nicotiana / Q000235:genetics
D018076:DNA, Complementary; D005630:Fructans; D010446:Peptide Fragments; D011994:Recombinant Proteins; D006602:Hexosyltransferases; C097181:sucrose - fructan 6-fructosyltransferase; D006026:Glycoside Hydrolases