2D04

Crystal structure of neoculin, a sweet protein with taste-modifying activity.

2D04 の概要

• エントリーDOI: 10.2210/pdb2d04/pdb
• 分子名称: neoculin acidic subunit, Curculin, beta-D-mannopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose-(1-4)-[beta-L-fucopyranose-(1-3)]2-acetamido-2-deoxy-beta-D-glucopyranose, ... (5 entities in total)
• 機能のキーワード: all beta, plant protein
• 由来する生物種: Curculigo latifolia (lumbah); 詳細
• タンパク質・核酸の鎖数: 8
• 化学式量合計: 100961.24

構造登録者

Shimizu-Ibuka, A.,Morita, Y.,Terada, T.,Asakura, T.,Nakajima, K.,Iwata, S.,Misaka, T.,Sorimachi, H.,Arai, S.,Abe, K. (登録日: 2005-07-25, 公開日: 2006-06-20, 最終更新日: 2024-10-30)

主引用文献

Shimizu-Ibuka, A.,Morita, Y.,Terada, T.,Asakura, T.,Nakajima, K.,Iwata, S.,Misaka, T.,Sorimachi, H.,Arai, S.,Abe, K.
Crystal structure of neoculin: insights into its sweetness and taste-modifying activity
J.Mol.Biol., 359:148-158, 2006

PubMed Abstract: Although the majority of sweet compounds are of low molecular mass, several proteins are known to elicit sweet taste responses in humans. The fruit of Curculigo latifolia contains a heterodimeric protein, neoculin, which has both sweetness and a taste-modifying activity that converts sourness to sweetness. Here, we report the crystal structure of neoculin at 2.76A resolution. This is the first well-defined tertiary structure of a taste-modifying protein of this kind. The overall structure is quite similar to those of monocot mannose-binding lectins. However, crucial topological differences are observed in the C-terminal regions of both subunits. In both subunits of neoculin, the C-terminal tails turn up to form loops fixed by inter-subunit disulfide bonds that are not observed in the lectins. Indeed, the corresponding regions of the lectins stretch straight over the surface of another subunit. Such a C-terminal structural feature as is observed in neoculin results in a decrease in subunit-subunit interactions. Moreover, distribution of electrostatic potential on the surface of neoculin is unique and significantly different from those of the lectins, particularly in the basic subunit (NBS). We have found that there is a large cluster composed of six basic residues on the surface of NBS, and speculate that it might be involved in the elicitation of sweetness and/or taste-modifying activity of neoculin. Molecular dynamics simulation based on the crystallography results suggests that neoculin may adopt a widely "open" conformation at acidic pH, while unprotonated neoculin at neutral pH is in a "closed" conformation. Based on these simulations and the generation of a docking model between neoculin and the sweet-taste receptor, T1R2-T1R3, we propose the hypothesis that neoculin is in dynamic equilibrium between open and closed states, and that the addition of an acid shifts the equilibrium to the open state, allowing ligand-receptor interaction.

PubMed: 16616933
DOI: 10.1016/j.jmb.2006.03.030

実験手法

X-RAY DIFFRACTION (2.76 Å)