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Bitterness, as one of the most important physiological sensations in animals, is primarily recognized through the mediation of bitter taste receptors. In recent years, it has been found that these receptors are not only expressed in taste bud cells on the tongue but also in the respiratory, cardiovascular, digestive, reproductive, and nervous systems. They are involved in regulating various fundamental physiological processes and are now considered important targets for the treatment of various diseases. This paper reviewed the structure, classification, distribution, and signaling pathways of bitter taste receptors, their relationship with different diseases, and the role of bitter taste receptors agonists, aiming to provide a basis for scientific research on bitter taste receptors.

In order to study the interaction between Pterocephalus hookeri and bitter taste receptors,three-dimensional structural models of bitter taste receptors TAS2 R16,TAS2 R14 and TAS2 R13 were established by homology modeling in this paper. Maestro software was used for docking the chemical constituents of P. hookeri with bitter taste receptors. The results showed that 25 chemical components of P. hookeri can regulate three bitter taste receptors. And these components were mainly iridoid glycosides and phenolic acids.This research focused on the comprehensive application of homology modeling and molecular docking technology to explore the interaction between bitter chemical constituents of P. hookeri and bitter taste receptors. This study provided assistance in revealing pharmacodynamic basis of bitter Tibetan medicine at molecular level. It also provided new ideas and methods for the study of Tibetan medicine.

Recognition of natural bitter toxins through taste is one of the most effective mechanisms of self-safety. An approximate 1 169 bp sequence of the bitter taste receptor T2R2 gene was obtained by PCR and cloning technique from hog badger genomic DNA(GenBank accession number: FJ812727). This sequence contains a complete single exon (without intron) 915 bp in size, which encodes 304 amino acid residues. The isoelectric point (pI) of the protein is 9.76 and its molecular weight is 34.74 kDa. Topology prediction showed that the T2R2 protein contained one N-glycosylation site, one N-myristoylation site, and two potential protein kinase C phosphorylation sites. Additionally, the whole peptide chain was comprised of seven transmembrane helix regions, four extracellular regions, and four intracellular regions. The T2R2 is a hydrophobic protein with a few hydrophilic components. Homology analysis of the T2R2 gene sequences by Clustal W indicated that the cDNA sequence homology of T2R2 gene in hog badger with dog, cat, cattle, horse, chimpanzee, and mouse is 91.4%, 90.6%, 84.4%, 85.4%, 83.8%and 72.1%, respectively, and the homology of amino acid sequence is 85.5%, 85.8%, 74.0%, 77.6%, 75.3% and 61.5%, respectively. The results of nucleotide acid substitution computation and selective test showed that strong purifying selection (functional constraint) occurred between hog badger and the six species, respectively, which mainly existed in the transmembrane regions of T2R2. In addition, the Neighbour-Joining tree of T2R2 gene exons from these seven species is consistent with their species tree, indicating that the T2R2 gene is suitable for constructing molecular phylogenetic tree among different species likewise.