seven-transmembrane G protein-coupled receptor superfamily; This hierarchical evolutionary model represents the seven-transmembrane (7TM) receptors, often referred to as G protein-coupled receptors (GPCRs), which transmit physiological signals from the outside of the cell to the inside via G proteins. GPCRs constitute the largest known superfamily of transmembrane receptors across the three kingdoms of life that respond to a wide variety of extracellular stimuli including peptides, lipids, neurotransmitters, amino acids, hormones, and sensory stimuli such as light, smell and taste. All GPCRs share 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. However, some 7TM receptors, such as the type 1 microbial rhodopsins, do not activate G proteins. Based on sequence similarity, GPCRs can be divided into six major classes: class A (the rhodopsin-like family), class B (the Methuselah-like, adhesion and secretin-like receptor family), class C (the metabotropic glutamate receptor family), class D (the fungal mating pheromone receptors), class E (the cAMP receptor family), and class F (the 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 550821993  71 ITIMALYSIVCVVGLFGNFLVMYVIV 96
Cdd:cd14970    1 IVIPAVYSVVCVVGLTGNSLVIYVIL 26

opioid receptors and related proteins, member of the class A family of seven-transmembrane G protein-coupled receptors; This group includes opioid receptors, somatostatin receptors, melanin-concentrating hormone receptors (MCHRs), and neuropeptides B/W receptors. Together they constitute the opioid receptor-like family, members of the class A G-protein coupled receptors. Opioid receptors are coupled to inhibitory G proteins of the G(i/o) family and are involved in regulating a variety of physiological functions such as pain, addiction, mood, stress, epileptic seizure, and obesity, among many others. G protein-coupled somatostatin receptors (SSTRs), which display strong sequence similarity with opioid receptors, binds somatostatin (somatotropin release inhibiting factor), a polypeptide hormone that regulates a wide variety of physiological functions such as neurotransmission, cell proliferation, contractility of smooth muscle cells, and endocrine signaling as well as inhibition of the release of many secondary hormones. MCHR binds melanin concentrating hormone and is presumably involved in the neuronal regulation of food intake. Despite strong homology with somatostatin receptors, MCHR does not appear to bind somatostatin. Neuropeptides B/W receptors are primarily expressed in the CNS and stimulate the cortisol secretion by activating the adenylate cyclase- and the phospholipase C-dependent signaling pathways.

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gi 550821993  71 ITIMALYSIVCVVGLFGNFLVMYVIV 96
Cdd:cd14970    1 IVIPAVYSVVCVVGLTGNSLVIYVIL 26

opioid receptors and related proteins, member of the class A family of seven-transmembrane G protein-coupled receptors; This group includes opioid receptors, somatostatin receptors, melanin-concentrating hormone receptors (MCHRs), and neuropeptides B/W receptors. Together they constitute the opioid receptor-like family, members of the class A G-protein coupled receptors. Opioid receptors are coupled to inhibitory G proteins of the G(i/o) family and are involved in regulating a variety of physiological functions such as pain, addiction, mood, stress, epileptic seizure, and obesity, among many others. G protein-coupled somatostatin receptors (SSTRs), which display strong sequence similarity with opioid receptors, binds somatostatin (somatotropin release inhibiting factor), a polypeptide hormone that regulates a wide variety of physiological functions such as neurotransmission, cell proliferation, contractility of smooth muscle cells, and endocrine signaling as well as inhibition of the release of many secondary hormones. MCHR binds melanin concentrating hormone and is presumably involved in the neuronal regulation of food intake. Despite strong homology with somatostatin receptors, MCHR does not appear to bind somatostatin. Neuropeptides B/W receptors are primarily expressed in the CNS and stimulate the cortisol secretion by activating the adenylate cyclase- and the phospholipase C-dependent signaling pathways.

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gi 550821993  71 ITIMALYSIVCVVGLFGNFLVMYVIV 96
Cdd:cd14970    1 IVIPAVYSVVCVVGLTGNSLVIYVIL 26

nociceptin/orphanin FQ peptide receptor, member of the class A family of seven-transmembrane G protein-coupled receptors; The nociceptin (NOP) receptor binds nociceptin or orphanin FQ, a 17 amino acid endogenous neuropeptide. The NOP receptor is involved in the modulation of various brain activities including instinctive and emotional behaviors. The opioid receptor family is composed of four major subtypes: mu (MOP), delta (DOP), kappa (KOP) opioid receptors, and the nociceptin/orphanin FQ peptide receptor (NOP). They are distributed widely in the central nervous system and respond to classic alkaloid opiates, such as morphine and heroin, as well as to endogenous peptide ligands, which include dynorphins, enkephalins, endorphins, endomorphins, and nociceptin. Opioid receptors are coupled to inhibitory G proteins of the G(i/o) family and involved in regulating a variety of physiological functions such as pain, addiction, mood, stress, epileptic seizure, and obesity, among many others.

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gi 550821993  71 ITIMALYSIVCVVGLFGNFLVMYVIV 96
Cdd:cd15092    1 VTIVVVYLIVCVVGLVGNCLVMYVIL 26

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 550821993  71 ITIMALYSIVCVVGLFGNFLVMYVI 95
Cdd:cd14993    1 IVLIVLYVVVFLLALVGNSLVIAVV 25

classical and atypical chemokine receptors, member of the class A family of seven-transmembrane G protein-coupled receptors; Chemokines are principal regulators for leukocyte trafficking, recruitment, and activation. Chemokine family membership is defined on the basis of sequence homology and on the presence of variations on a conserved cysteine motif, which allows the family to further divide into four subfamilies (CC, CXC, XC, and CX3C). Chemokines interact with seven-transmembrane receptors which are typically coupled to G protein for signaling. Currently, there are ten known receptors for CC chemokines, seven for CXC chemokines, and single receptors for the XC and CX3C chemokines. In addition to these classical chemokine receptors, there exists a subfamily of atypical chemokine receptors (ACKRs) that are unable to couple to G-proteins and, instead, they preferentially mediate beta-arrestin dependent processes, such as receptor internalization, after ligand binding. The classical chemokine receptors contain a conserved DRYLAIV motif in the second intracellular loop, which is required for G-protein coupling. However, the ACKRs lack this conserved motif and fail to couple to G-proteins and induce classical GPCR signaling. Five receptors have been identified for the ACKR family, including CC-chemokine receptors like 1 and 2 (CCRL1 and CCRL2), CXCR7, Duffy antigen receptor for chemokine (DARC), and D6. Both ACKR1 (DARC) and ACKR3 (CXCR7) show low sequence homology to the classic chemokine receptors.

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gi 550821993  75 ALYSIVCVVGLFGNFLVMYVIVS 97
Cdd:cd14984    5 VLYSLVFLLGLVGNSLVLLVLLY 27

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 550821993  71 ITIMALYSIVCVVGLFGNFLVMYVIV 96
Cdd:cd15203    1 IILILLYGLIIVLGVVGNLLVIYVVL 26

Epstein-Barr virus (EBV)-induced gene 2, member of the class A family of seven-transmembrane G protein-coupled receptors; Epstein-Barr virus-induced G-protein coupled receptor 2 (EBI2), also called GPR183, is activated by 7alpha, 25-dihydroxyxcholesterol (7alpha, 25-OHC), an oxysterol. EBI2 was originally identified as one of major genes induced in the Burkitt's lymphoma cell line BL41by EBV infection. EBI2 is involved in regulating B cell migration and responses, and is also implicated in human diseases such as type I diabetes, multiple sclerosis, and cancers.

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gi 550821993  71 ITIMALYSIVCVVGLFGNFLVMYVIVS 97
Cdd:cd15159    1 VLLPLFYSLILVFGLLGNTLALHVICQ 27

somatostatin-like receptor for allatostatin C, member of the class A family of seven-transmembrane G protein-coupled receptors; G protein-coupled somatostatin receptors (SSTRs) are composed of five distinct subtypes (SSTR1-5) that display strong sequence similarity with opioid receptors. All five receptor subtypes bind the natural somatostatin (somatotropin release inhibiting factor), a polypeptide hormone that regulates a wide variety of physiological functions such as neurotransmission, cell proliferation, contractility of smooth muscle cells, and endocrine signaling as well as inhibition of the release of many secondary hormones. In Drosophila melanogaster and other insects, a 15-amino-acid peptide named allatostatin C(AstC) binds the somatostatin-like receptors. Two AstC receptors have been identified in Drosophila with strong sequence homology to human somatostatin and opioid receptors.

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gi 550821993  76 LYSIVCVVGLFGNFLVMYVI 95
Cdd:cd15094    6 LYGLICIVGLVGNGLVIYVV 25

melanin concentrating hormone receptor, member of the class A family of seven-transmembrane G protein-coupled receptors; Melanin-concentrating hormone receptor (MCHR) binds melanin concentrating hormone and is presumably involved in the neuronal regulation of food intake and energy homeostasis. Despite strong homology with somatostatin receptors, MCHR does not appear to bind somatostatin. Two MCHRs have been characterized in vertebrates, MCHR1 and MCHR2. MCHR1 is expressed in all mammals, whereas MCHR2 is only expressed in the higher order mammals, such as humans, primates, and dogs, and is not found in rodents. 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 550821993  71 ITIMALYSIVCVVGLFGNFLVMYVIV 96
Cdd:cd15088    1 VIMPSVFGCICVVGLVGNGIVLYVLV 26

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 550821993  73 IMALYSIVCVVGLFGNFLVMYVIV 96
Cdd:cd00637    1 LAVLYILIFVVGLVGNLLVILVIL 24

G protein-coupled receptor 83, member of the class A family of seven-transmembrane G protein-coupled receptors; GPR83, also known as GPR72, is widely expressed in the brain, including hypothalamic nuclei which is involved in regulating energy balance and food intake. The hypothalamic expression of GPR83 is tightly regulated in response to nutrient availability and is decreased in obese mice. A recent study suggests that GPR83 has a critical role in the regulation of systemic energy metabolism via ghrelin-dependent and ghrelin-independent mechanisms. GPR83 shares a significant amino acid sequence identity with the tachykinin receptors, however its endogenous ligand is unknown.

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gi 550821993  73 IMALYSIVCVVGLFGNFLVMYVIV 96
Cdd:cd15389    3 LIVAYSIIIVISLFGNSLVCHVIF 26