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Design of taste-modifying molecules based on the analysis of the structure and function of taste-modifying protein, curculin.

基于口味调节蛋白仙茅素的结构和功能的分析，设计口味调节分子。

基本信息

批准号：
18590101
负责人：
KURIMOTO Eiji
金额：
$ 2.32万
依托单位：
Nagoya City University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2006
资助国家：
日本
起止时间：
2006 至 2007
项目状态：
已结题

项目摘要

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.The site responsible for the taste-modifying activity includes His-36 in the curculin2 subunit. It is possible that the protonation of this histidine residue triggers the activation of the T1R2-T1R3-mediated signal transduction. Supporting this idea, the pH dependence of the taste-modifying activity of the curculin1-2 heterodimer was in good agreement with that of the protonation of His-36 of the curculin2 subunit examined by NMR spectroscopy.

从马来西亚种植的Curculigo宽叶植物中分离出的Curculin具有一种耐人寻味的特性，可以将酸味变成甜味。除了这种改善口感的活动外，仙茅蛋白本身也能产生甜味。虽然这些活性被归因于Curculin的异二聚体而不是同源二聚体，但这种蛋白双重作用的潜在机制仍然很不清楚。为了确定这些活性的关键位点，我们对重组culculin进行了突变和结构研究。在比较其晶体结构的基础上，设计了一系列突变体并进行了品尝试验。根据突变效应将氨基酸残基映射到三维结构上，结果表明，仙茅蛋白杂二聚体通过其部分重叠但截然不同的分子表面显示出甜味和调味活性。这些发现表明，culculin异源二聚体的两种活性是通过其与T1R2-T1R3异源二聚体甜味受体的两种不同相互作用模式表达的。负责味觉调节活性的位置包括curculin2亚基中的His-36。这种组氨酸残基的质子化可能触发了T1R2-T1R3介导的信号转导的激活。支持这一观点的是，Curculin1-2异二聚体的味觉调节活性的pH依赖关系与核磁共振光谱检测到的curculin2亚基的His-36质子化的依赖关系很好地一致。