7 transmembrane receptor (rhodopsin family); This family contains, amongst other G-protein-coupled receptors (GCPRs), members of the opsin family, which have been considered to be typical members of the rhodopsin superfamily. They share several motifs, mainly the seven transmembrane helices, GCPRs of the rhodopsin superfamily. All opsins bind a chromophore, such as 11-cis-retinal. The function of most opsins other than the photoisomerases is split into two steps: light absorption and G-protein activation. Photoisomerases, on the other hand, are not coupled to G-proteins - they are thought to generate and supply the chromophore that is used by visual opsins.

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                  ....*....|....*....|....*....|....*....|....*....|....
gi 77025070     5 WSLAFLAFERYMVICKPF-GNFRFSPKHALMVVLATWTIGIGVSVPP-FFGWSR 56
Cdd:pfam00001  74 LLLTAISIDRYLAIVHPLrYKRRRTPRRAKVLILVIWVLALLLSLPPlLFGWTL 127

short wave-sensitive 2 opsins, member of the class A family of seven-transmembrane G protein-coupled receptors; This group includes Short Wave-Sensitive opsin 2 (SWS2), which mediates visual transduction in response to light at short wavelengths (violet to blue). Vertebrate cone opsins are expressed in cone photoreceptor cells of the retina and involved in mediating photopic vision, which allows color perception. The cone opsins can be classified into four classes according to their peak absorption wavelengths: SWS1 (ultraviolet sensitive), SWS2 (short wave-sensitive), MWS/LWS (medium/long wave-sensitive), and RH2 (medium wave-sensitive, rhodopsin-like opsins). Members of this group belong to the class A of the G protein-coupled receptors and possess seven-transmembrane (TM) alpha-helices interconnected by three extracellular and three intracellular loops.

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                ....*....|....*....|....*....|....*....|....*....|....*.
gi 77025070   1 LVTGWSLAFLAFERYMVICKPFGNFRFSPKHALMVVLATWTIGIGVSVPPFFGWSR 56
Cdd:cd15077  85 MVSLWSLAVVAFERFLVICKPLGNFTFRGTHAIIGCIATWVFGLAASLPPLFGWSR 140

type 2 opsins in animals, member of the class A family of seven-transmembrane G protein-coupled receptors; This rhodopsin family represents the type 2 opsins found in vertebrates and invertebrates except sponge. Type 2 opsins primarily function as G protein coupled receptors and are responsible for vision as well as for circadian rhythm and pigment regulation. On the contrary, type 1 opsins such as bacteriorhodopsin and proteorhodopsin are found in both prokaryotic and eukaryotic microbes, functioning as light-gated ion channels, proton pumps, sensory receptors and in other unknown functions. Although these two opsin types share seven-transmembrane domain topology and a conserved lysine reside in the seventh helix, type 1 opsins do not activate G-proteins and are not evolutionarily related to type 2. Type 2 opsins can be classified into six distinct subfamilies including the vertebrate opsins/encephalopsins, the G(o) opsins, the G(s) opsins, the invertebrate G(q) opsins, the photoisomerases, and the neuropsins.

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gi 77025070   1 LVTGWSLAFLAFERYMVICKPFGNFRFSPKHALMVVLATWTIGIGVSVPPFFGWSR 56
Cdd:cd14969  85 LVSISTLAALAFERYLVIVRPLKAFRLSKRRALILIAFIWLYGLFWALPPLFGWSS 140

non-visual VA (vertebrate ancient) opsins, member of the class A family of seven-transmembrane G protein-coupled receptors; The vertebrate ancient (VA) opsin photopigments were originally identified in salmon and they appear to have diverged early in the evolution of vertebrate opsins. VA opsins are localized in the inner retina and the brain in teleosts. The vertebrate non-visual opsin family includes pinopsins, parapinopsin, VA (vertebrate ancient) opsins, and parietopsins. These non-visual opsins are expressed in various extraretinal tissues and/or in non-rod, non-cone retinal cells. They are thought to be involved in light-dependent physiological functions such as photo-entrainment of circadian rhythm, photoperiodicity, and body color change. The VA opsins belong the class A of the G protein-coupled receptors and possess seven-transmembrane (TM) alpha-helices interconnected by three extracellular and three intracellular loops.

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gi 77025070   1 LVTGWSLAFLAFERYMVICKPFGNFRFSPKHALMVVLATWTIGIGVSVPPFFGWSR 56
Cdd:cd15082  98 IVALWSLAVLAFERFFVICRPLGNIRLQGKHAALGLLFVWTFSFIWTIPPVLGWSS 153

insect photoreceptors R1-R6 and similar proteins, member of the class A family of seven-transmembrane G protein-coupled receptors; This group includes the insect photoreceptors and their closely related proteins. The Drosophila eye is composed of about 800 unit eyes called ommatidia, each of which contains eight photoreceptor cells (R1-R8). The six outer photoreceptors (R1-R6) function like the vertebrate rods and are responsible for motion detection in dim light and image formation. The R1-R6 photoreceptors express a blue-absorbing pigment, Rhodopsin 1(Rh1). The inner photoreceptors (R7 and R8) are considered the equivalent of the color-sensitive vertebrate cone cells, which express a range of different pigments. The R7 photoreceptors express one of two different UV absorbing pigments, either Rh3 or Rh4. Likewise, the R8 photoreceptors express either the blue absorbing pigment Rh5 or green absorbing pigment Rh6. These photoreceptors belong the class A of the G protein-coupled receptors and possess seven-transmembrane (TM) alpha-helices interconnected by three extracellular and three intracellular loops.

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gi 77025070   2 VTGWSLAFLAFERYMVICKPFGNFRFSPKHALMVVLATWTIGIGVSVPPF-FGWSR 56
Cdd:cd15079  85 GSIWTNAAIAYDRYNVIVKPLNGNPLTRGKALLLILFIWLYALPWALLPLlFGWGR 140

non-visual parietopsins, member of the class A family of seven-transmembrane G protein-coupled receptors; Parietopsin is a non-visual green light-sensitive opsin that was initially identified in the parietal eye of lizards. The vertebrate non-visual opsin family includes pinopsins, parapinopsin, VA (vertebrate ancient) opsins, and parietopsins. These non-visual opsins are expressed in various extra-retinal tissues and/or in non-rod, non-cone retinal cells. They are thought to be involved in light-dependent physiological functions such as photo-entrainment of circadian rhythm, photoperiodicity and body color change. Parietopsin belongs to the class A of the G protein-coupled receptors and shows strong homology to the vertebrate visual opsins.

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gi 77025070   1 LVTGWSLAFLAFERYMVICKPFGNFRFSPKHALMVVLATWTIGIGVSVPPFFGWS 55
Cdd:cd15085  85 IVSLWSLTLLAYERYNVVCKPMGGLKLSTKRGYQGLLFIWLFCLFWAVAPLFGWS 139

rhodopsin receptor-like class A family of the seven-transmembrane G protein-coupled receptor superfamily; Class A rhodopsin-like receptors constitute about 90% of all GPCRs. The class A GPCRs include the light-sensitive rhodopsin as well as receptors for biogenic amines, lipids, nucleotides, odorants, peptide hormones, and a variety of other ligands. All GPCRs have a common structural architecture comprising of seven-transmembrane (TM) alpha-helices interconnected by three extracellular and three intracellular loops. A general feature of GPCR signaling is agonist-induced conformational changes in the receptors, leading to activation of the heterotrimeric G proteins, which consist of the guanine nucleotide-binding G-alpha subunit and the dimeric G-beta-gamma subunits. The activated G proteins then bind to and activate numerous downstream effector proteins, which generate second messengers that mediate a broad range of cellular and physiological processes. Based on sequence similarity, GPCRs can be divided into six major classes: class A (rhodopsin-like family), class B (Methuselah-like, adhesion and secretin-like receptor family), class C (metabotropic glutamate receptor family), class D (fungal mating pheromone receptors), class E (cAMP receptor family), and class F (frizzled/smoothened receptor family). Nearly 800 human GPCR genes have been identified and are involved essentially in all major physiological processes. Approximately 40% of clinically marketed drugs mediate their effects through modulation of GPCR function for the treatment of a variety of human diseases including bacterial infections.

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gi 77025070   1 LVTGWSLAFLAFERYMVICKPF-GNFRFSPKHALMVVLATWTIGIGVSVPPFFGWSR 56
Cdd:cd00637  83 LASILTLTAISVDRYLAIVHPLrYRRRFTRRRAKLLIALIWLLSLLLALPPLLGWGV 139

neuropsin (Opsin-5), member of the class A family of seven-transmembrane G protein-coupled receptors; Neuropsin, also known as Opsin-5, is a photoreceptor protein expressed in the retina, brain, testes, and spinal cord. Neuropsin belongs to the type 2 opsin family of the class A G-protein coupled receptors. Mammalian neuropsin activates Gi protein-mediated photo-transduction pathway in a UV-dependent manner, whereas, in non-mammalian vertebrates, neuropsin is involved in regulating the photoperiodic control of seasonal reproduction in birds such as quail. As with other opsins, it may also act as a retinal photoisomerase.

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gi 77025070   1 LVTGWSLAFLAFERYMVICKPFGNFRFSPKHALMVVLATWTIGIGVSVPPFFGWSR 56
Cdd:cd15074  85 CCSINTLTAISIYRYLKICHPPYGPKLSRRHVCIVIVAIWLYALFWAVAPLVGWGS 140

neuropeptide Y receptors and related proteins, member of the class A family of seven-transmembrane G protein-coupled receptors; NPY is a 36-amino acid peptide neurotransmitter with a C-terminal tyrosine amide residue that is widely distributed in the brain and the autonomic nervous system of many mammalian species. NPY exerts its functions through five, G-protein coupled receptor subtypes including NPY1R, NPY2R, NPY4R, NPY5R, and NPY6R; however, NPY6R is not functional in humans. NYP receptors are also activated by its two other family members, peptide YY (PYY) and pancreatic polypeptide (PP). They typically couple to Gi or Go proteins, which leads to a decrease in adenylate cyclase activity, thereby decreasing intracellular cAMP levels, and are involved in diverse physiological roles including appetite regulation, circadian rhythm, and anxiety. Also included in this subgroup is prolactin-releasing peptide (PrRP) receptor (previously known as GPR10), which is activated by its endogenous ligand PrRP, a neuropeptide possessing C-terminal Arg-Phe-amide motif. There are two active isoforms of PrRP in mammals: one consists of 20 amino acid residues (PrRP-20) and the other consists of 31 amino acid residues (PrRP-31). PrRP receptor shows significant sequence homology to the NPY receptors, and a micromolar level of NPY can bind and completely inhibit the PrRP-evoked intracellular calcium response in PrRP receptor-expressing cells, suggesting that the PrRP receptor shares a common ancestor with the NPY receptors.

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gi 77025070   2 VTGWSLAFLAFERYMVICKPFGNfRFSPKHALMVVLATWTIGIGVSVPPFF 52
Cdd:cd15203  86 VSTLTLTAIAIDRYQLIVYPTRP-RMSKRHALLIIALIWILSLLLSLPLAI 135

serotonin receptor subtypes 1, 5 and 7, member of the class A family of seven-transmembrane G protein-coupled receptors; This group includes serotonin receptor subtypes 1, 5, and 7 that are activated by the neurotransmitter serotonin. The 5-HT1 and 5-HT5 receptors mediate inhibitory neurotransmission by coupling to G proteins of the G(i/o) family. The 5-HT1 receptor subfamily includes 5-HT1A, 5-HT1B, 5-HT1D, 5-HT1E, and 5-HT1F. There is no 5-HT1C receptor subtype, as it has been reclassified as 5-HT2C receptor. The 5-HT5A and 5-HT5B receptors have been cloned from rat and mouse, but only the 5-HT5A isoform has been identified in human because of the presence of premature stop codons in the human 5-HT5B gene, which prevents a functional receptor from being expressed. The 5-HT7 receptor is coupled to Gs, which positively stimulates adenylate cyclase activity, leading to increased intracellular cAMP formation and calcium influx. In the CNS, serotonin is involved in the regulation of appetite, mood, sleep, cognition, learning and memory, as well as implicated in neurologic disorders such as migraine, schizophrenia, and depression.

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gi 77025070   5 WSLAFLAFERYMVICKP--FGNFRfSPKHALMVVLATWTIGIGVSVPPFFGWS 55
Cdd:cd15064  89 LHLCVIALDRYWAITDAveYAHKR-TPKRAAVMIALVWTLSICISLPPLFGWR 140

cholecystokinin receptors and related proteins, member of the class A family of seven-transmembrane G protein-coupled receptors; This group represents four G-protein coupled receptors that are members of the RFamide receptor family, including cholecystokinin receptors (CCK-AR and CCK-BR), orexin receptors (OXR), neuropeptide FF receptors (NPFFR), and pyroglutamylated RFamide peptide receptor (QRFPR). These RFamide receptors are activated by their endogenous peptide ligands that share a common C-terminal arginine (R) and an amidated phenylanine (F) motif. CCK-AR (type A, alimentary; also known as CCK1R) is found abundantly on pancreatic acinar cells and binds only sulfated CCK-peptides with very high affinity, whereas CCK-BR (type B, brain; also known as CCK2R), the predominant form in the brain and stomach, binds CCK or gastrin and discriminates poorly between sulfated and non-sulfated peptides. CCK is implicated in regulation of digestion, appetite control, and body weight, and is involved in neurogenesis via CCK-AR. There is some evidence to support that CCK and gastrin, via their receptors, are involved in promoting cancer development and progression, acting as growth and invasion factors. Orexins (OXs; also referred to as hypocretins) are neuropeptide hormones that regulate the sleep-wake cycle and potently influence homeostatic systems regulating appetite and feeding behavior or modulating emotional responses such as anxiety or panic. OXs are synthesized as prepro-orexin (PPO) in the hypothalamus and then proteolytically cleaved into two forms of isoforms: orexin-A (OX-A) and orexin-B (OX-B). OXA is a 33 amino-acid peptide with N-terminal pyroglutamyl residue and two intramolecular disulfide bonds, whereas OXB is a 28 amino-acid linear peptide with no disulfide bonds. OX-A binds orexin receptor 1 (OX1R) with high-affinity, but also binds with somewhat low-affinity to OX2R, and signals primarily to Gq coupling, whereas OX-B shows a strong preference for the orexin receptor 2 (OX2R) and signals through Gq or Gi/o coupling. The 26RFa, also known as QRFP (Pyroglutamylated RFamide peptide), is a 26-amino acid residue peptide that exerts similar orexigenic activity including the regulation of feeding behavior in mammals. It is the ligand for G-protein coupled receptor 103 (GPR103), which is predominantly expressed in paraventricular (PVN) and ventromedial (VMH) nuclei of the hypothalamus. GPR103 shares significant protein sequence homology with orexin receptors (OX1R and OX2R), which have recently shown to produce a neuroprotective effect in Alzheimer's disease by forming a functional heterodimer with GPR103. Neuropeptide FF (NPFF) is a mammalian octapeptide that has been implicated in a wide range of physiological functions in the brain including pain sensitivity, insulin release, food intake, memory, blood pressure, and opioid-induced tolerance and hyperalgesia. The effects of NPFF are mediated through neuropeptide FF1 and FF2 receptors (NPFF1-R and NPFF2-R) which are predominantly expressed in the brain. NPFF induces pro-nociceptive effects, mainly through the NPFF1-R, and anti-nociceptive effects, mainly through the NPFF2-R.

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gi 77025070   5 WSLAFLAFERYMVICKPFGNFRFSPK-HALMVVLATWTIGIGVSVP 49
Cdd:cd14993  89 LTLVAISIDRYLAICYPLKARRVSTKrRARIIIVAIWVIAIIIMLP 134

vasopressin and oxytocin receptors, member of the class A family of seven-transmembrane G protein-coupled receptors; Vasopressin (also known as arginine vasopressin or anti-diuretic hormone) and oxytocin are synthesized in the hypothalamus and are released from the posterior pituitary gland. The actions of vasopressin are mediated by the interaction of this hormone with three receptor subtypes: V1aR, V1bR, and V2R. These subtypes are differ in localization, function, and signaling pathways. Activation of V1aR and V1bR stimulate phospholipase C, while activation of V2R stimulates adenylate cyclase. Although vasopressin and oxytocin differ only by two amino acids and stimulate the same cAMP/PKA pathway, they have divergent physiological functions. Vasopressin is involved in regulating blood pressure and the balance of water and sodium ions, whereas oxytocin plays an important role in the uterus during childbirth and in lactation.

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gi 77025070   7 LAFLAFERYMVICKPFGNFRFSPKHALMVVLATWTIGIGVSVPPFFGWS 55
Cdd:cd15196  91 LVATAIDRYIAICHPLSSHRWTSRRVHLMVAIAWVLSLLLSIPQLFIFS 139

adenosine receptor subfamily, member of the class A family of seven-transmembrane G protein-coupled receptors; The adenosine receptors (or P1 receptors), a family of G protein-coupled purinergic receptors, bind adenosine as their endogenous ligand. There are four types of adenosine receptors in human, designated as A1, A2A, A2B, and A3. Each type is encoded by a different gene and has distinct functions with some overlap. For example, both A1 and A2A receptors are involved in regulating myocardial oxygen consumption and coronary blood flow in the heart, while the A2A receptor also has a broad spectrum of anti-inflammatory effects in the body. These two receptors also expressed in the brain, where they have important roles in the release of other neurotransmitters such as dopamine and glutamate, while the A2B and A3 receptors found primarily in the periphery and play important roles in inflammation and immune responses. The A1 and A3 receptors preferentially interact with G proteins of the G(i/o) family, thereby lowering the intracellular cAMP levels, whereas the A2A and A2B receptors interact with G proteins of the G(s) family, activating adenylate cyclase to elevate cAMP levels.

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gi 77025070   6 SLAFLAFERYMVICKPFGNFRF-SPKHALMVVLATWTIGIGVSVPPFFGW 54
Cdd:cd14968  88 SLLAIAIDRYLAIKIPLRYKSLvTGRRAWGAIAVCWVLSFLVGLTPMFGW 137

relaxin receptor 2 (or LGR8), member of the class A family of seven-transmembrane G protein-coupled receptors; Relaxin is a member of the insulin superfamily that has diverse actions in both reproductive and non-reproductive tissues. The relaxin-like peptide family includes relaxin-1, relaxin-2, and the insulin-like (INSL) peptides such as INSL3, INSL4, INSL5 and INSL6. The relaxin family peptides share high structural similarity, but low sequence similarity, and exert their physiological functions by activating a group of four G protein-coupled receptors, RXFP1-4. INSL3 is the endogenous ligand for RXFP2, which couples to the G(s) protein to increase intracellular cAMP levels, but also to the GoB protein to decrease cAMP formation. RXFP2 (or LGR8) is expressed in various tissues including the brain, kidney, muscle, testis, thyroid, uterus, and peripheral blood cells, among others.

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gi 77025070   7 LAFLAFERYMVICKPFGNFRFSPKHALMVVLATWTIGIGVSVPPFF 52
Cdd:cd15966  98 LTYLTLEKYLVIVFPFSNIRPGKCQTLIILISIWLVGFIIAVIPFW 143

serotonin receptor subtype 2C, member of the class A family of seven-transmembrane G protein-coupled receptors; The 5-HT2 receptors are a subfamily of serotonin receptors that bind the neurotransmitter serotonin (5HT; 5-hydroxytryptamine) in the central nervous system (CNS). The 5-HT2 subfamily is composed of three subtypes that mediate excitatory neurotransmission: 5-HT2A, 5-HT2B, and 5-HT2C. They are selectively linked to G proteins of the G(q/11) family and activate phospholipase C, which leads to activation of protein kinase C and calcium release. In the CNS, serotonin is involved in the regulation of appetite, mood, sleep, cognition, learning and memory, as well as implicated in diseases such as migraine, schizophrenia, and depression. Indeed, 5-HT2 receptors are attractive targets for a variety of psychoactive drugs, ranging from atypical antipsychotic drugs, antidepressants, and anxiolytics, which have an antagonistic action on 5-HT2 receptors, to hallucinogens, which act as agonists at postsynaptic 5-HT2 receptors. All GPCRs have a common structural architecture comprising of seven-transmembrane (TM) alpha-helices interconnected by three extracellular and three intracellular loops. A general feature of GPCR signaling is agonist-induced conformational changes in the receptors, leading to activation of the heterotrimeric G proteins, which consist of the guanine nucleotide-binding G-alpha subunit and the dimeric G-beta-gamma subunits. The activated G proteins then bind to and activate numerous downstream effector proteins, which generate second messengers that mediate a broad range of cellular and physiological processes.

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gi 77025070   7 LAFLAFERYMVICKPFGNFRFSPK-HALMVVLATWTIGIGVSVP 49
Cdd:cd15305  92 LCAISLDRYVAIRNPIEHSRFNSRtKAMMKIAAVWTISIGISMP 135

teleost multiple tissue (tmt) opsin, member of the class A family of seven-transmembrane G protein-coupled receptors; Teleost multiple tissue (tmt) opsins are homologs of encephalopsin. Mouse encephalopsin (or panopsin) is highly expressed in the brain and testes, whereas the teleost homologs are localized to multiple tissues. The exact functions of the encephalopsins and tmt-opsins are unknown. The vertebrate non-visual opsin family includes pinopsins, parapinopsin, VA (vertebrate ancient) opsins, and parietopsins. These non-visual opsins are expressed in various extra-retinal tissues and/or in non-rod, non-cone retinal cells. They are thought to be involved in light-dependent physiological functions such as photo-entrainment of circadian rhythm, photoperiodicity and body color change. Tmt opsins belong to the class A of the G protein-coupled receptors and show strong homology to the vertebrate visual opsins.

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gi 77025070   6 SLAFLAFERYMVICKPFGNFRFSPKHALMVVLATWTIGIGVSVPPFFGWSR 56
Cdd:cd15086  90 SLAVLSYERYCTLLRPTEADVSDYRKAWLGVGGSWLYSLLWTLPPLLGWSS 140

FMRFamide (Phe-Met-Arg-Phe) receptors and related proteins, member of the class A family of seven-transmembrane G protein-coupled receptors; This group includes Drosophila melanogaster G-protein coupled FMRFamide (Phe-Met-Arg-Phe-NH2) receptor DrmFMRFa-R and related invertebrate receptors, as well as the vertebrate proteins GPR139 and GPR142. DrmFMRFa-R binds with high affinity to FMRFamide and intrinsic FMRFamide-related peptides. FMRFamide is a neuropeptide from the family of FMRFamide-related peptides (FaRPs), which all containing a C-terminal RFamide (Arg-Phe-NH2) motif and have diverse functions in the central and peripheral nervous systems. FMRFamide is an important neuropeptide in many types of invertebrates such as insects, nematodes, molluscs, and worms. In invertebrates, the FMRFamide-related peptides are involved in the regulation of heart rate, blood pressure, gut motility, feeding behavior, and reproduction. On the other hand, in vertebrates such as mice, they play a role in the modulation of morphine-induced antinociception. Orphan receptors GPR139 and GPR142 are very closely related G protein-coupled receptors, but they have different expression patterns in the brain and in other tissues. These receptors couple to inhibitory G proteins and activate phospholipase C. Studies suggested that dimer formation may be required for their proper function. GPR142 is predominantly expressed in pancreatic beta-cells and mediates enhancement of glucose-stimulated insulin secretion, whereas GPR139 is mostly expressed in the brain and is suggested to play a role in the control of locomotor activity. Tryptophan and phenylalanine have been identified as putative endogenous ligands of GPR139.

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gi 77025070   5 WSLAFLAFERYMVICKPF-GNFRFSPKHALMVVLATWTIGIGVSVPPFF 52
Cdd:cd14978  93 WLTVALTVERYIAVCHPLkARTWCTPRRARRVILIIIIFSLLLNLPRFF 141

G protein-coupled receptor 39, member of the class A family of seven-transmembrane G protein-coupled receptors; GPR39 is an orphan G protein-coupled receptor that belongs to the growth hormone secretagogue and neurotensin receptor subfamily. GPR39 is expressed in peripheral tissues such as pancreas, gut, gastrointestinal tract, liver, kidney as well as certain regions of the brain. The divalent metal ion Zn(2+) has been shown to be a ligand capable of activating GPR39. Thus, it has been suggested that GPR39 function as a G(q)-coupled Zn(2+)-sensing receptor which involved in the regulation of endocrine pancreatic function, body weight, gastrointestinal mobility, and cell death.

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gi 77025070   7 LAFLAFERYMVICKPFGNFRFSPKHALMVVLATWTIGIGVSVPPFF 52
Cdd:cd15135  96 VATLSFERYIAICHPFKYKALSGSRVRLLICFVWLTSALVALPLLF 141

olfactory receptor family 4 and related proteins, member of the class A family of seven-transmembrane G protein-coupled receptors; This group includes human olfactory receptor family 4 and related proteins in other mammals, sauropsids, and amphibians. Olfactory receptors (ORs) play a central role in olfaction, the sense of smell. ORs belong to the class A rhodopsin-like family of G protein-coupled receptors and constitute the largest multigene family in mammals of approximately 1,000 genes. More than 60% of human ORs are non-functional pseudogenes compared to only 20% in mouse. Each OR can recognize structurally similar odorants, and a single odorant can be detected by several ORs. Binding of an odorant to the olfactory receptor induces a conformational change that leads to the activation of the olfactory-specific G protein (Golf). The G protein (Golf and/or Gs) in turn stimulates adenylate cyclase to make cAMP. The cAMP opens cyclic nucleotide-gated ion channels, which allow the influx of calcium and sodium ions, resulting in depolarization of the olfactory receptor neuron and triggering an action potential which transmits this information to the brain. A consensus nomenclature system based on evolutionary divergence is used here to classify the olfactory receptor family. The nomenclature begins with the root name OR, followed by an integer representing a family, a letter denoting a subfamily, and an integer representing the individual gene within the subfamily.

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gi 77025070   7 LAFLAFERYMVICKPFGNFRF-SPKHALMVVLATWTIGI 44
Cdd:cd15226  91 LIAMAFDRYVAICKPLHYLTImSPRMCILLVVASWIIGF 129