Department of Molecular Genetics, German Institute of Human Nutrition Potsdam-Rehbruecke, 14558 Nuthetal, Germany.
J Neurosci. 2013 Jan 2;33(1):201-13. doi: 10.1523/JNEUROSCI.3248-12.2013.
Bitter taste is a basic taste modality, required to safeguard animals against consuming toxic substances. Bitter compounds are recognized by G-protein-coupled bitter taste receptors (TAS2Rs). The human TAS2R10 responds to the toxic strychnine and numerous other compounds. The mechanism underlying the development of the broad tuning of some TAS2Rs is not understood. Using comparative modeling, site-directed mutagenesis, and functional assays, we identified residues involved in agonist-induced activation of TAS2R10, and investigated the effects of different substitutions on the receptor's response profile. Most interestingly, mutations in S85(3.29) and Q175(5.40) have differential impact on stimulation with different agonists. The fact that single point mutations lead to improved responses for some agonists and to decreased activation by others indicates that the binding site has evolved to optimally accommodate multiple agonists at the expense of reduced potency. TAS2R10 shares the agonist strychnine with TAS2R46, another broadly tuned receptor. Engineering the key determinants for TAS2R46 activation by strychnine in TAS2R10 caused a loss of response to strychnine, indicating that these paralog receptors display different strychnine-binding modes, which suggests independent acquisition of agonist specificities. This implies that the gene duplication event preceding primate speciation was accompanied by independent evolution of the strychnine-binding sites.
苦味是一种基本的味觉模式，对于保护动物免受有毒物质的侵害至关重要。苦味化合物被 G 蛋白偶联的苦味受体（TAS2R）识别。人类 TAS2R10 对有毒的士的宁和许多其他化合物有反应。然而，一些 TAS2R 产生广泛调谐的机制尚不清楚。我们通过比较建模、定点突变和功能测定，确定了参与 TAS2R10 激动剂诱导激活的残基，并研究了不同取代对受体反应谱的影响。最有趣的是，S85（3.29）和 Q175（5.40）残基的突变对不同激动剂的刺激有不同的影响。事实上，单个点突变导致一些激动剂的反应增强，而对其他激动剂的激活作用降低，这表明结合位点已经进化到可以最佳地适应多种激动剂，而牺牲了效力。TAS2R10 与另一个广泛调谐的受体 TAS2R46 共享激动剂士的宁。在 TAS2R10 中对 TAS2R46 激活的关键决定因素进行工程改造，导致对士的宁的反应丧失，这表明这些同源受体表现出不同的士的宁结合模式，这表明它们具有不同的特异性。这意味着在灵长类动物分化之前的基因复制事件伴随着士的宁结合位点的独立进化。
