Purification and complete amino acid sequence of a new type of sweet protein taste-modifying activity, curculin.
A new taste-modifying protein named curculin was extracted with 0.5 M NaCl from the fruits of Curculigo latifolia and purified by ammonium sulfate fractionation, CM-Sepharose ion-exchange chromatography, and gel filtration. Purified curculin thus obtained gave a single band having a Mr of 12,000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis in the presence of 8 M urea. The molecular weight determined by low-angle laser light scattering was 27,800. These results suggest that native curculin is a dimer of a 12,000-Da polypeptide. The complete amino acid sequence of curculin was determined by automatic Edman degradation. Curculin consists of 114 residues. Curculin itself elicits a sweet taste. After curculin, water elicits a sweet taste, and sour substances induce a stronger sense of sweetness. No protein with both sweet-tasting and taste-modifying activities has ever been found. There are five sets of tripeptides common to miraculin (a taste-modifying protein), six sets of tripeptides common to thaumatin (a sweet protein), and two sets of tripeptides common to monellin (a sweet protein). Anti-miraculin serum was not immunologically reactive with curculin. The mechanism of the taste-modifying action of curculin is discussed.
Department of Chemistry, Faculty of Education, Yokohama National University, Japan.
H
H
Yamashita
S
S
Theerasilp
T
T
Aiuchi
K
K
Nakaya
Y
Y
Nakamura
Y
Y
Kurihara
D000595:Amino Acid Sequence; D006801:Humans; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010446:Peptide Fragments / Q000302:isolation & purification; D010940:Plant Proteins / Q000302:isolation & purification*; D011487:Protein Conformation; D013649:Taste; D014675:Vegetables / Q000032:analysis*
D010446:Peptide Fragments; D010940:Plant Proteins; C065630:curculin