ID:GNAT3_HUMAN DESCRIPTION: RecName: Full=Guanine nucleotide-binding protein G(t) subunit alpha-3; AltName: Full=Gustducin alpha-3 chain; FUNCTION: Guanine nucleotide-binding protein (G protein) alpha subunit playing a prominent role in bitter and sweet taste transduction as well as in umami (monosodium glutamate, monopotassium glutamate, and inosine monophosphate) taste transduction. Transduction by this alpha subunit involves coupling of specific cell-surface receptors with a cGMP-phosphodiesterase; Activation of phosphodiesterase lowers intracellular levels of cAMP and cGMP which may open a cyclic nucleotide-suppressible cation channel leading to influx of calcium, ultimately leading to release of neurotransmitter. Indeed, denatonium and strychnine induce transient reduction in cAMP and cGMP in taste tissue, whereas this decrease is inhibited by GNAT3 antibody. Gustducin heterotrimer transduces response to bitter and sweet compounds via regulation of phosphodiesterase for alpha subunit, as well as via activation of phospholipase C for beta and gamma subunits, with ultimate increase inositol trisphosphate and increase of intracellular Calcium. GNAT3 can functionally couple to taste receptors to transmit intracellular signal: receptor heterodimer TAS1R2/TAS1R3 senses sweetness and TAS1R1/TAS1R3 transduces umami taste, whereas the T2R family GPCRs act as bitter sensors. Functions also as lumenal sugar sensors in the gut to control the expression of the Na+-glucose transporter SGLT1 in response to dietaty sugar, as well as the secretion of Glucagon-like peptide- 1, GLP-1 and glucose-dependent insulinotropic polypeptide, GIP. Thus, may modulate the gut capacity to absorb sugars, with implications in malabsorption syndromes and diet-related disorders including diabetes and obesity. SUBUNIT: G proteins are composed of 3 units; alpha, beta and gamma, respectively GNAT3, GNB1 and GNG13 for Gustducin heterotrimer for bitter taste transduction. The alpha chain contains the guanine nucleotide binding site. Gustducin heterotrimer may also be composed of GNAT3, GNB3 and GNG13. SUBCELLULAR LOCATION: Cytoplasm. Note=Dual ditribution pattern; plasmalemmal pattern with apical region localization and cytosolic pattern with localization throughout the cytoplasm. TISSUE SPECIFICITY: Expressed in taste buds (sensory organs of clustered epithelial cells) of the circumvallate and foliate papillae of the tongue at protein level. Expressed in enteroendocrine L cells of the gut. Detected also in spermatozoa. PTM: Potential N-myristoylation may anchor alpha-subunit to the inner surface of plasma membrane (By similarity). SIMILARITY: Belongs to the G-alpha family. G(i/o/t/z) subfamily. SEQUENCE CAUTION: Sequence=EAL24192.1; Type=Erroneous gene model prediction; Sequence=EAL24193.1; Type=Erroneous gene model prediction;
The RNAfold program from the Vienna RNA Package is used to perform the secondary structure predictions and folding calculations. The estimated folding energy is in kcal/mol. The more negative the energy, the more secondary structure the RNA is likely to have.
ModBase Predicted Comparative 3D Structure on A8MTJ3
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Orthologous Genes in Other Species
Orthologies between human, mouse, and rat are computed by taking the best BLASTP hit, and filtering out non-syntenic hits. For more distant species reciprocal-best BLASTP hits are used. Note that the absence of an ortholog in the table below may reflect incomplete annotations in the other species rather than a true absence of the orthologous gene.
Protein A8MTJ3 (Reactome details) participates in the following event(s):
R-HSA-8850560 G-protein alpha releases G-protein heterotrimer from PDCL R-HSA-392206 G alpha (i) inhibits adenylate cyclase R-HSA-392212 G alpha (i) auto-inactivates by hydrolysing GTP to GDP R-HSA-392202 Dissociation of the P2Y purinoceptor 12:Gi complex R-HSA-749454 The Ligand:GPCR:Gi complex dissociates R-HSA-751001 Inactive G alpha (i) reassociates with G beta:gamma R-HSA-170674 Dissociation of the Gi alpha:G olf complex R-HSA-167433 G-protein beta-gamma subunits rebind the alpha-GDP subunit R-HSA-112037 Inactivation of PLC beta R-HSA-167415 G-protein alpha subunit is inactivated R-HSA-111870 Activation of PLC beta-1/4 R-HSA-112271 The receptor:G-protein complex dissociates R-HSA-167429 The receptor:G-protein complex binds GTP R-HSA-170671 G alpha-olf:GTP binds to Gi alpha1:GTP:adenylate cyclase complex R-HSA-170686 Adenylate cyclase increases the GTPase activity of Gi alpha R-HSA-392187 Activated P2Y purinoceptor 12 binds G-protein Gi R-HSA-749456 Liganded Gi-activating GPCRs bind inactive heterotrimeric G-protein Gi R-HSA-167408 The high affinity receptor complex binds to G-protein R-HSA-167419 The receptor:G-protein complex releases GDP R-HSA-392195 Gi activation by P2Y purinoceptor 12 R-HSA-380073 Liganded Gi-activating GPCR acts as a GEF for Gi R-HSA-170666 Adenylate cyclase increases the GTPase activity of G alpha-olf R-HSA-111879 PIP2 hydrolysis R-HSA-6814122 Cooperation of PDCL (PhLP1) and TRiC/CCT in G-protein beta folding R-HSA-170670 Adenylate cyclase inhibitory pathway R-HSA-418594 G alpha (i) signalling events R-HSA-392170 ADP signalling through P2Y purinoceptor 12 R-HSA-202040 G-protein activation R-HSA-112043 PLC beta mediated events R-HSA-390466 Chaperonin-mediated protein folding R-HSA-112040 G-protein mediated events R-HSA-997269 Inhibition of adenylate cyclase pathway R-HSA-388396 GPCR downstream signalling R-HSA-392518 Signal amplification R-HSA-111885 Opioid Signalling R-HSA-391251 Protein folding R-HSA-991365 Activation of GABAB receptors R-HSA-372790 Signaling by GPCR R-HSA-76002 Platelet activation, signaling and aggregation R-HSA-392499 Metabolism of proteins R-HSA-977444 GABA B receptor activation R-HSA-162582 Signal Transduction R-HSA-109582 Hemostasis R-HSA-977443 GABA receptor activation R-HSA-112314 Neurotransmitter receptors and postsynaptic signal transmission R-HSA-112315 Transmission across Chemical Synapses R-HSA-112316 Neuronal System
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Common Gene Haplotype Alleles 
