Research in polymorphisms in human taste receptor genes and taste disorder

T2 R包含G蛋白偶联受体超家族，其含有功能上定义的苦味受体。我们在染色体7 q31上的人类T2 R基因（hT 2 R3、hT 2 R4和hT 2 R5）中发现编码单核苷酸多态性（cSNP）。我们在T2 R受体基因中鉴定了6个cSNP。hT 2 R4和hT 2 R5分别包含4个和1个引起错义突变的cSNP，而hT 2 R3包含1个沉默核苷酸突变。然而，我们没有发现任何无义突变，导致移码或提前终止密码子内的开放阅读框架。T2 R受体和G蛋白α亚基（Gα），gustducin，被认为是其感知的关键分子，但对其相互作用的分子基础知之甚少。我们使用异源表达系统来确定T2 R偶联所需的gustducin的特定结构域。两种嵌合Gα16蛋白在其C末端分别含有37和44个gustducin特异性序列（G16/gust 37和G16/gust 44），它们对具有已知配体的不同T2 R受体有反应，但G16/gust 23、G16/gust 11和G16/gust 5没有反应。前两种嵌合体均含有预期的β6折叠结构域、α5螺旋结构域和味觉蛋白C末端结构域，这些结构域都是T2 R活性表达所必需的。我们还表达了G16蛋白嵌合体，其具有来自其他Gαi蛋白的相应结构域，锥细胞转导蛋白（Gαt2）、Gαi2和Gαz（G16/t2、G16/i2和G16/z）。结果表明，G16/t2和G16/i2产生了T2 R的特异性反应，而G16/z没有。使用基于Gα16的嵌合体和hT 2 R16变体，我们检查了对水杨苷的敏感性。人类T2 R受体的核苷酸多样性和氨基酸多态性的鉴定可以帮助澄清对苦味化合物的接受性和敏感性的个体差异。

T2Rs comprise a G-protein-coupled receptor superfamily that contains functionally defined bitter taste receptors. We found coding single-nucleotide polymorphisms (cSNPs) in human T2R genes (hT2R3, hT2R4, and hT2R5) on chromosome 7q31. We identified six cSNPs within the T2R receptor genes. The hT2R4 and hT2R5 contained four and on cSNPs that cause missense mutations, respectively, while hT2R3 included one silent nucleotide mutation. However, we could not find any nonsense mutations that resulted in a frameshift or a premature stop codon within the open reading frames. T2R receptors and a G-protein α subunit (Gα), gustducin, are believed to be key molecules for its perception, but little is known about the molecular basis for its interaction. We use a heterologous expression system to determine a specific domain of gustducin necessary for T2R coupling. Two chimeric Gα16 proteins harboring 37 and 44 gustducin-specific sequences at their C termini (G16/gust37 and G16/gust44) responded to different T2R receptors with known ligands, but G16/gust23, G16/gust11, and G16/gust5 did not. The former two chimeras contained a predicted β6 sheet, an α5 helix, and an extreme C terminus of gustducin, and all the domains were indispensable to the expression of T2R activity. We also expressed G16 protein chimeras with the corresponding domain from other Gαi proteins, cone-transducin (Gαt2), Gαi2, and Gαz (G16/t2, G16/i2, and G16/z). As a result, G16/t2 and G16/i2 produced specific responses of T2Rs, but G16/z did not. Using Gα16-based chimeras and hT2R16 variants, we examined sensitivity to salicin. Identification of nucleotide diversity and amino acid polymorphisms in human T2R receptors could help clarify individual differences in the acceptability and sensitivity to bitter compounds.