title: Curculin exhibits sweet-tasting and taste-modifying activities through its distinct molecular surfaces.
abstract: Curculin isolated from Curculigo latifolia, a plant grown in Malaysia, has an intriguing property of modifying sour taste into sweet taste. In addition to this taste-modifying activity, curculin itself elicits a sweet taste. Although these activities have been attributed to the heterodimeric isoform and not homodimers of curculin, the underlying mechanisms for the dual action of this protein have been largely unknown. To identify critical sites for these activities, we performed a mutational and structural study of recombinant curculin. Based on the comparison of crystal structures of curculin homo- and heterodimers, a series of mutants was designed and subjected to tasting assays. Mapping of amino acid residues on the three-dimensional structure according to their mutational effects revealed that the curculin heterodimer exhibits sweet-tasting and taste-modifying activities through its partially overlapping but distinct molecular surfaces. These findings suggest that the two activities of the curculin heterodimer are expressed through its two different modes of interactions with the T1R2-T1R3 heterodimeric sweet taste receptor.
authors: Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe-dori, Mizuho-ku, Nagoya 467-8603.
authors: Eiji
authors: E
authors: Kurimoto
authors: Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe-dori, Mizuho-ku, Nagoya 467-8603.
authors: Maiko
authors: M
authors: Suzuki
authors: Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe-dori, Mizuho-ku, Nagoya 467-8603.
authors: Eiko
authors: E
authors: Amemiya
authors: Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe-dori, Mizuho-ku, Nagoya 467-8603.
authors: Yoshiki
authors: Y
authors: Yamaguchi
authors: Enzyme Laboratory, National Food Research Institute, 2-1-12 Kannondai, Tsukuba 305-8642, Ibaraki.
authors: Satoru
authors: S
authors: Nirasawa
authors: Institute of Life Sciences, Ajinomoto Co., Inc., 1-1 Suzuki-cho, Kawasaki-ku, Kawasaki 210-8681.
authors: Nobuhisa
authors: N
authors: Shimba
authors: Institute of Life Sciences, Ajinomoto Co., Inc., 1-1 Suzuki-cho, Kawasaki-ku, Kawasaki 210-8681.
authors: Ningchun
authors: N
authors: Xu
authors: Institute of Life Sciences, Ajinomoto Co., Inc., 1-1 Suzuki-cho, Kawasaki-ku, Kawasaki 210-8681.
authors: Tatsuki
authors: T
authors: Kashiwagi
authors: Institute of Life Sciences, Ajinomoto Co., Inc., 1-1 Suzuki-cho, Kawasaki-ku, Kawasaki 210-8681.
authors: Misako
authors: M
authors: Kawai
authors: Institute of Life Sciences, Ajinomoto Co., Inc., 1-1 Suzuki-cho, Kawasaki-ku, Kawasaki 210-8681.
authors: Ei-Ichiro
authors: EI
authors: Suzuki
authors: Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe-dori, Mizuho-ku, Nagoya 467-8603; Institute for Molecular Science, National Institutes of Natural Sciences, 5-1 Higashiyama, Myodaiji, Okazaki, Aichi 444-8787, Japan. Electronic address: kkato@phar.nagoya-cu.ac.jp.
authors: Koichi
authors: K
authors: Kato
mesh_terms: D001665:Binding Sites; D031408:Curculigo / Q000378:metabolism; D019281:Dimerization; D004926:Escherichia coli / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008958:Models, Molecular; D008968:Molecular Conformation; D009154:Mutation; D010940:Plant Proteins / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology*; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D013649:Taste
chemical_list: D010940:Plant Proteins; C065630:curculin