A putative receptor protein in the taste receptor of the fly.

Protein T1R3, the main subunit of sweet, as well as amino acid, taste receptor, is expressed in the epithelium of the tongue and gastro intestinal tract, in β–cells of the pancreas, hypothalamus, and numerous other organs. Recently, convincing witnesses of T1R3 involvement in control of carbohydrate and lipid metabolism, and control of production of incretines and insulin, have been determined. In the study on Tas1r3-gene knockout mouse strain and parent strain C57Bl/6J as control, priority data concerning the effect of T1R3 on the morphological characteristics of Langerhans islets in the pancreas, are obtained. In Tas1r3 knockout animals, it is found that the size of the islets and their density in pancreatic tissue are reduced, as compared to the parent strain. Additionally, a decrease of expression of active caspase-3 in islets of gene-knockouts is demonstrated. The obtained data show that the lack of a functional, gene encoding sweet-taste receptor protein causes a dystrophy of the islet tissue and associates to the development of pathological changes in the pancreas specific to type-2 diabetes and obesity in humans.

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Sequence and Structural Diversity of the S Locus Genes From Different Lines With the Same Self-Recognition Specificities in Brassica oleracea

Genetics ◽

10.1093/genetics/154.1.413 ◽

2000 ◽

Vol 154 (1) ◽

pp. 413-420 ◽

Cited By ~ 2

Author(s):

Makoto Kusaba ◽

Masanori Matsushita ◽

Keiichi Okazaki ◽

Yoko Satta ◽

Takeshi Nishio

Keyword(s):

Structural Diversity ◽

Receptor Protein ◽

Self Incompatibility ◽

S Locus ◽

High Similarity ◽

Putative Receptor ◽

Recognition Specificity ◽

Polymorphic Genes ◽

Self Recognition ◽

Self Fertilization

Abstract Self-incompatibility (SI) is a mechanism for preventing self-fertilization in flowering plants. In Brassica, it is controlled by a single multi-allelic locus, S, and it is believed that two highly polymorphic genes in the S locus, SLG and SRK, play central roles in self-recognition in stigmas. SRK is a putative receptor protein kinase, whose extracellular domain exhibits high similarity to SLG. We analyzed two pairs of lines showing cross-incompatibility (S2 and S2-b; S13 and S13-b). In S2 and S2-b, SRKs were more highly conserved than SLGs. This was also the case with S13 and S13-b. This suggests that the SRKs of different lines must be conserved for the lines to have the same self-recognition specificity. In particular, SLG2-b showed only 88.5% identity to SLG2, which is comparable to that between the SLGs of different S haplotypes, while SRK2-b showed 97.3% identity to SRK2 in the S domain. These findings suggest that the SLGs in these S haplotypes are not important for self-recognition in SI.

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Regulation of the Putative TRPV1t Salt Taste Receptor by Phosphatidylinositol 4, 5-Bisphosphate

Journal of Neurophysiology ◽

10.1152/jn.00883.2009 ◽

2010 ◽

Vol 103 (3) ◽

pp. 1337-1349 ◽

Cited By ~ 17

Author(s):

Vijay Lyall ◽

Tam-Hao T. Phan ◽

ZuoJun Ren ◽

Shobha Mummalaneni ◽

Pamela Melone ◽

...

Keyword(s):

Monosodium Glutamate ◽

Taste Receptor ◽

Receptor Protein ◽

Chorda Tympani ◽

Sprague Dawley ◽

Salt Taste ◽

Sprague Dawley Rats ◽

Enhanced Ct ◽

Biphasic Effect ◽

Phosphatidylinositol 4

Regulation of the putative amiloride and benzamil (Bz)-insensitive TRPV1t salt taste receptor by phosphatidylinositol 4,5-bisphosphate (PIP2) was studied by monitoring chorda tympani (CT) taste nerve responses to 0.1 M NaCl solutions containing Bz (5 × 10−6 M; a specific ENaC blocker) and resiniferatoxin (RTX; 0–10 × 10−6 M; a specific TRPV1 agonist) in Sprague-Dawley rats and in wildtype (WT) and TRPV1 knockout (KO) mice. In rats and WT mice, RTX elicited a biphasic effect on the NaCl + Bz CT response, increasing the CT response between 0.25 × 10−6 and 1 × 10−6 M. At concentrations >1 × 10−6 M, RTX inhibited the CT response. An increase in PIP2 by topical lingual application of U73122 (a phospholipase C blocker) or diC8-PIP2 (a short chain synthetic PIP2) inhibited the control NaCl + Bz CT response and decreased its sensitivity to RTX. A decrease in PIP2 by topical lingual application of phenylarsine oxide (a phosphoinositide 4 kinase blocker) enhanced the control NaCl + Bz CT response, increased its sensitivity to RTX stimulation, and inhibited the desensitization of the CT response at RTX concentrations >1 × 10−6 M. The ENaC-dependent NaCl CT responses were not altered by changes in PIP2. An increase in PIP2 enhanced CT responses to sweet (0.3 M sucrose) and bitter (0.01 M quinine) stimuli. RTX produced the same increase in the Bz-insensitive Na+response when present in salt solutions containing 0.1 M NaCl + Bz, 0.1 M monosodium glutamate + Bz, 0.1 M NaCl + Bz + 0.005 M SC45647, or 0.1 M NaCl + Bz + 0.01 M quinine. No effect of RTX was observed on CT responses in WT mice and rats in the presence of the TRPV1 blocker N-(3-methoxyphenyl)-4-chlorocinnamide (1 × 10−6 M) or in TRPV1 KO mice. We conclude that PIP2 is a common intracellular effector for sweet, bitter, umami, and TRPV1t-dependent salt taste, although in the last case, PIP2 seems to directly regulate the taste receptor protein itself, i.e., the TRPV1 ion channel or its taste receptor variant, TRPV1t.

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Ultimate Molecular Theory of Bitter Taste

10.26434/chemrxiv.13622423.v1 ◽

2021 ◽

Author(s):

Huazhong He

Keyword(s):

Binding Sites ◽

Bitter Taste ◽

Taste Receptor ◽

Sweet Taste ◽

Receptor Protein ◽

Helical Structures ◽

Sweet Taste Receptor ◽

Multiple Binding Sites ◽

Multiple Receptors ◽

Multiple Binding

More than thirty years ago, I proposed a theory about sweet and bitter molecules’ recognition by protein helical structures. Unfortunately the papers could not go to public platform until now. Inspired by the sweet taste theory<sup>1,2</sup>, this bitter taste theory conveys that bitter molecules are recognized by receptor protein helical structures. The recognition process is a dynamic action, in which the receptor protein helices have a torsion-spring-like oscillation between helical structures of 3.6 and 4 amino acids per turn. Based on the characteristics of the bitter receptor protein helix oscillation, it perfectly explains why in bitter molecules, only one unit of hydrogen donor (DH) or hydrogen acceptor (B) is enough in helping molecules to elicit bitter taste. The potential DH and B in bitter receptor are any NH or O of receptor’s peptide NHs and Os, which are the ones forming intramolecular H-bonds responsible for the formation of receptor protein helical structures. Furthermore, only one unit of DH or B is allowed for structurally simple ligands. As recognition sites are only associated with a small fraction – helix structure of whole bitter receptor, multiple binding sites or multiple receptors are well expected. As the oscillation may have different extent, it translates to bitterness intensity. According to ligand-receptor binding motion, bitter receptor could be divided into two kinds of spaces, which are similar to the situation in sweet taste receptor: main and side grooves. These have been discussed in context and especially great details in paper titled deciphering aspartyl peptide sweeteners <sup>2</sup>.

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The Arabidopsis ERECTA Gene Encodes a Putative Receptor Protein Kinase with Extracellular Leucine-Rich Repeats

The Plant Cell ◽

10.2307/3870348 ◽

1996 ◽

Vol 8 (4) ◽

pp. 735 ◽

Cited By ~ 2

Author(s):

Keiko U. Torii ◽

Norihiro Mitsukawa ◽

Teruko Oosumi ◽

Yutaka Matsuura ◽

Ryusuke Yokoyama ◽

...

Keyword(s):

Protein Kinase ◽

Receptor Protein ◽

Putative Receptor ◽

Erecta Gene ◽

Leucine Rich Repeats

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High-performance swCNT-FET-based bioelectronic tongue using human taste receptor protein

Journal of Bioscience and Bioengineering ◽

10.1016/j.jbiosc.2009.08.407 ◽

2009 ◽

Vol 108 ◽

pp. S152

Author(s):

Hyun Seok Song ◽

Tae Hyun Kim ◽

Sang Hun Lee ◽

Un-Kyung Kim ◽

Seunghun Hong ◽

...

Keyword(s):

High Performance ◽

Taste Receptor ◽

Receptor Protein

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Differential scanning fluorimetric analysis of the amino-acid binding to taste receptor using a model receptor protein, the ligand-binding domain of fish T1r2a/T1r3

10.1101/670828 ◽

2019 ◽

Author(s):

Takashi Yoshida ◽

Norihisa Yasui ◽

Yuko Kusakabe ◽

Chiaki Ito ◽

Miki Akamatsu ◽

...

Keyword(s):

Amino Acids ◽

Amino Acid ◽

Ligand Binding ◽

Taste Receptor ◽

Thermal Stabilization ◽

Receptor Protein ◽

Binding Characteristics ◽

Melting Temperatures ◽

Binding Domains ◽

Amino Acid Binding

AbstractTaste receptor type 1 (T1r) is responsible for the perception of essential nutrients, such as sugars and amino acids, and evoking sweet and umami (savory) taste sensations. T1r receptors recognize many of the taste substances at their extracellular ligand-binding domains (LBDs). In order to detect a wide array of taste substances in the environment, T1r receptors often possess broad ligand specificities. However, the entire ranges of chemical spaces and their binding characteristics to any T1rLBDs have not been extensively analyzed. In this study, we exploited the differential scanning fluorimetry (DSF) to medaka T1r2a/T1r3LBD, a current sole T1rLBD heterodimer amenable for recombinant preparation, and analyzed their thermal stabilization by adding various amino acids. The assay showed that the agonist amino acids induced thermal stabilization and shifted the melting temperatures (Tm) of the protein. An agreement between the DSF results and the previous biophysical assay was observed, suggesting that DSF can detect ligand binding at the orthosteric-binding site in T1r2a/T1r3LBD. The assay further demonstrated that most of the tested L-amino acids, but no D-amino acid, induced Tm shifts of T1r2a/T1r3LBD, indicating the broad L-amino acid specificities of the proteins probably with several different manners of recognition. The Tm shifts by each amino acid also showed a fair correlation with the responses exhibited by the full-length receptor, verifying the broad amino-acid binding profiles at the orthosteric site in LBD observed by DSF.

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Molecular cloning of a putative receptor protein kinase gene encoded at the self-incompatibility locus of Brassica oleracea.

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.88.19.8816 ◽

1991 ◽

Vol 88 (19) ◽

pp. 8816-8820 ◽

Cited By ~ 387

Author(s):

J. C. Stein ◽

B. Howlett ◽

D. C. Boyes ◽

M. E. Nasrallah ◽

J. B. Nasrallah

Keyword(s):

Protein Kinase ◽

Brassica Oleracea ◽

Molecular Cloning ◽

The Self ◽

Receptor Protein ◽

Self Incompatibility ◽

Kinase Gene ◽

Putative Receptor ◽

Protein Kinase Gene ◽

Incompatibility Locus

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T1r3 taste receptor involvement in gustatory neural responses to ethanol and oral ethanol preference

Physiological Genomics ◽

10.1152/physiolgenomics.00113.2009 ◽

2010 ◽

Vol 41 (3) ◽

pp. 232-243 ◽

Cited By ~ 24

Author(s):

Susan M. Brasser ◽

Meghan B. Norman ◽

Christian H. Lemon

Keyword(s):

Taste Receptor ◽

Sweet Taste ◽

Receptor Protein ◽

Wild Type ◽

Ethanol Preference ◽

Background Strain ◽

Neurobiological Substrates ◽

High Concentrations ◽

Gustatory Neurons ◽

Deficient Mice

Elevated alcohol consumption is associated with enhanced preference for sweet substances across species and may be mediated by oral alcohol-induced activation of neurobiological substrates for sweet taste. Here, we directly examined the contribution of the T1r3 receptor protein, important for sweet taste detection in mammals, to ethanol intake and preference and the neural processing of ethanol taste by measuring behavioral and central neurophysiological responses to oral alcohol in T1r3 receptor-deficient mice and their C57BL/6J background strain. T1r3 knockout and wild-type mice were tested in behavioral preference assays for long-term voluntary intake of a broad concentration range of ethanol, sucrose, and quinine. For neurophysiological experiments, separate groups of mice of each genotype were anesthetized, and taste responses to ethanol and stimuli of different taste qualities were electrophysiologically recorded from gustatory neurons in the nucleus of the solitary tract. Mice lacking the T1r3 receptor were behaviorally indifferent to alcohol (i.e., ∼50% preference values) at concentrations typically preferred by wild-type mice (5–15%). Central neural taste responses to ethanol in T1r3-deficient mice were significantly lower compared with C57BL/6J controls, a strain for which oral ethanol stimulation produced a concentration-dependent activation of sweet-responsive NTS gustatory neurons. An attenuated difference in ethanol preference between knockouts and controls at concentrations >15% indicated that other sensory and/or postingestive effects of ethanol compete with sweet taste input at high concentrations. As expected, T1r3 knockouts exhibited strongly suppressed behavioral and neural taste responses to sweeteners but did not differ from wild-type mice in responses to prototypic salt, acid, or bitter stimuli. These data implicate the T1r3 receptor in the sensory detection and transduction of ethanol taste.

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