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.

                         10        20        30        40        50
                 ....*....|....*....|....*....|....*....|....*....|....*
gi 763708771   1 VQIALSDHLKQRREVAKTVFCLVLVFALCWLPLHLSRILKLTIYDEKDPNRCELL 55
Cdd:cd15976  206 MQIALNDHLKQRREVAKTVFCLVLVFALCWLPLHLSRILKLTIYDEKDPNRCELL 260

endothelin B receptor, member of the class A family of seven-transmembrane G protein-coupled receptors; Endothelins are able to activate a number of signal transduction processes including phospholipase A2, phospholipase C, and phospholipase D, as well as cytosolic protein kinase activation. They play an important role in the regulation of the cardiovascular system and are the most potent vasoconstrictors identified, stimulating cardiac contraction, regulating the release of vasoactive substances, and stimulating mitogenesis in blood vessels. Two endothelin receptor subtypes have been isolated and identified in vertebrates, endothelin A receptor (ET-A) and endothelin B receptor (ET-B), and are members of the seven transmembrane class A G-protein coupled receptor family which activate multiple effectors via different types of G protein. Some vertebrates contain a third subtype, endothelin A receptor (ET-C). ET-A receptors are mainly located on vascular smooth muscle cells, whereas ET-B receptors are present on endothelial cells lining the vessel wall. Endothelin receptors have also been found in the brain.

                         10        20        30        40        50
                 ....*....|....*....|....*....|....*....|....*....|....*
gi 763708771   1 VQIALSDHLKQRREVAKTVFCLVLVFALCWLPLHLSRILKLTIYDEKDPNRCELL 55
Cdd:cd15976  206 MQIALNDHLKQRREVAKTVFCLVLVFALCWLPLHLSRILKLTIYDEKDPNRCELL 260

G protein-coupled chemokine receptor-like protein; Provisional

                         10        20        30
                 ....*....|....*....|....*....|
gi 763708771  10 KQRREVAKTVFCLVLVFALCWLPLHLSRIL 39
Cdd:PHA03087 237 KKNKKAIKLVLIIVILFVIFWLPFNVSVFV 266

endothelin B receptor, member of the class A family of seven-transmembrane G protein-coupled receptors; Endothelins are able to activate a number of signal transduction processes including phospholipase A2, phospholipase C, and phospholipase D, as well as cytosolic protein kinase activation. They play an important role in the regulation of the cardiovascular system and are the most potent vasoconstrictors identified, stimulating cardiac contraction, regulating the release of vasoactive substances, and stimulating mitogenesis in blood vessels. Two endothelin receptor subtypes have been isolated and identified in vertebrates, endothelin A receptor (ET-A) and endothelin B receptor (ET-B), and are members of the seven transmembrane class A G-protein coupled receptor family which activate multiple effectors via different types of G protein. Some vertebrates contain a third subtype, endothelin A receptor (ET-C). ET-A receptors are mainly located on vascular smooth muscle cells, whereas ET-B receptors are present on endothelial cells lining the vessel wall. Endothelin receptors have also been found in the brain.

                         10        20        30        40        50
                 ....*....|....*....|....*....|....*....|....*....|....*
gi 763708771   1 VQIALSDHLKQRREVAKTVFCLVLVFALCWLPLHLSRILKLTIYDEKDPNRCELL 55
Cdd:cd15976  206 MQIALNDHLKQRREVAKTVFCLVLVFALCWLPLHLSRILKLTIYDEKDPNRCELL 260

endothelin A (or endothelin-1) receptor, member of the class A family of seven-transmembrane G protein-coupled receptors; Endothelins are able to activate a number of signal transduction processes including phospholipase A2, phospholipase C, and phospholipase D, as well as cytosolic protein kinase activation. They play an important role in the regulation of the cardiovascular system and are the most potent vasoconstrictors identified, stimulating cardiac contraction, regulating the release of vasoactive substances, and stimulating mitogenesis in blood vessels. Two endothelin receptor subtypes have been isolated and identified in vertebrates, endothelin A receptor (ET-A) and endothelin B receptor (ET-B), and are members of the seven transmembrane class A G-protein coupled receptor family which activate multiple effectors via different types of G protein. Some vertebrates contain a third subtype, endothelin A receptor (ET-C). ET-A receptors are mainly located on vascular smooth muscle cells, whereas ET-B receptors are present on endothelial cells lining the vessel wall. Endothelin receptors have also been found in the brain.

                         10        20        30        40        50
                 ....*....|....*....|....*....|....*....|....*....|....*
gi 763708771   1 VQIALSDHLKQRREVAKTVFCLVLVFALCWLPLHLSRILKLTIYDEKDPNRCELL 55
Cdd:cd15975  210 LRIALSEHLKQRREVAKTVFCLVVIFALCWFPLHLSRILKKTVYNENDPRRCELL 264

endothelin receptors and related proteins, member of the class A family of seven-transmembrane G protein-coupled receptors; This subfamily of G-protein coupled receptors includes endothelin receptors, bombesin receptor subtype 3 (BRS-3), gastrin-releasing peptide receptor (GRPR), neuromedin B receptor (NMB-R), endothelin B receptor-like 2 (ETBR-LP-2), and GRP37. The endothelin receptors and related proteins are members of the seven transmembrane rhodopsin-like G-protein coupled receptor family (class A GPCRs) which activate multiple effectors via different types of G protein.

                         10        20        30        40
                 ....*....|....*....|....*....|....*....|....*
gi 763708771   2 QIALSDHLKQRREVAKTVFCLVLVFALCWLPLHLSRILKLTIYDE 46
Cdd:cd14977  206 TRGTKKHMKQRRQLAKTVLCLVLVFAFCWLPEHISNILRATLYNE 250

bombesin receptor subfamily, member of the class A family of seven-transmembrane G protein-coupled receptors; This bombesin subfamily of G-protein coupled receptors consists of neuromedin B receptor (NMBR), gastrin-releasing peptide receptor (GRPR), and bombesin receptor subtype 3 (BRS-3). Bombesin is a tetradecapeptide, originally isolated from frog skin. Mammalian bombesin-related peptides are widely distributed in the gastrointestinal and central nervous systems. The bombesin family receptors couple mainly to the G proteins of G(q/11) family. NMBR functions as the receptor for the neuropeptide neuromedin B, a potent mitogen and growth factor for normal and cancerous lung and for gastrointestinal epithelial tissues. Gastrin-releasing peptide is an endogenous ligand for GRPR and shares high sequence homology with NMB in the C-terminal region. Both NMB and GRP possess bombesin-like biochemical properties. BRS-3 is classified as an orphan receptor and suggested to play a role in sperm cell division and maturation. BRS-3 interacts with known naturally-occurring bombesin-related peptides with low affinity; however, no endogenous high-affinity ligand to the receptor has been identified. The bombesin receptor family belongs to the seven transmembrane rhodopsin-like G-protein coupled receptors (class A GPCRs), which perceive extracellular signals and transduce them to guanine nucleotide-binding (G) proteins.

                         10        20
                 ....*....|....*....|....
gi 763708771  12 RREVAKTVFCLVLVFALCWLPLHL 35
Cdd:cd15927  219 RKKVAKTVLAFVVLFAVCWLPRHV 242

KiSS1-derived peptide (kisspeptin) receptor, member of the class A family of seven-transmembrane G protein-coupled receptors; The G protein-coupled KiSS1-derived peptide receptor (GPR54 or kisspeptin receptor) binds the peptide hormone kisspeptin (previously known as metastin), which encoded by the metastasis suppressor gene (KISS1) expressed in various endocrine and reproductive tissues. The KiSS1 receptor is coupled to G proteins of the G(q/11) family, which lead to activation of phospholipase C and increase of intracellular calcium. This signaling cascade plays an important role in reproduction by regulating the secretion of gonadotropin-releasing hormone.

                         10        20
                 ....*....|....*....|....*...
gi 763708771   8 HLKQRREVAKTVFCLVLVFALCWLPLHL 35
Cdd:cd15095  211 ALRQKRKVTRMVIVVVVLFAICWLPNHV 238

neuromedin U receptor subtype 1, member of the class A family of seven-transmembrane G protein-coupled receptors; Neuromedin U (NMU) is a highly conserved neuropeptide with a common C-terminal heptapeptide sequence (FLFRPRN-amide) found at the highest levels in the gastrointestinal tract and pituitary gland of mammals. Disruption or replacement of residues in the conserved heptapeptide region can result in the reduced ability of NMU to stimulate smooth-muscle contraction. Two G-protein coupled receptor subtypes, NMU-R1 and NMU-R2, with a distinct expression pattern, have been identified to bind NMU. NMU-R1 is expressed primarily in the peripheral nervous system, while NMU-R2 is mainly found in the central nervous system. Neuromedin S, a 36 amino-acid neuropeptide that shares a conserved C-terminal heptapeptide sequence with NMU, is a highly potent and selective NMU-R2 agonist. Pharmacological studies have shown that both NMU and NMS inhibit food intake and reduce body weight, and that NMU increases energy expenditure.

                         10        20        30        40
                 ....*....|....*....|....*....|....*....|....*..
gi 763708771   3 IALSDHLKQRREVAKTVFCLVLVFALCWLPLHLSRILKLTIYDEKDP 49
Cdd:cd15358  221 RRIQQEKRRRRQVTKMLFVLVVVFGICWAPFHTDRLMWSFISQWTGE 267

neuropeptide FF receptors, member of the class A family of seven-transmembrane G protein-coupled receptors; Neuropeptide FF (NPFF) is a mammalian octapeptide that belongs to a family of neuropeptides containing an RF-amide motif at their C-terminus that have 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 these peptides 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. NPFF has been shown to inhibit adenylate cyclase via the Gi protein coupled to NPFF1-R.

                         10        20        30
                 ....*....|....*....|....*....|....*.
gi 763708771   4 ALSDHLKQRREVAKTVFCLVLVFALCWLPLHLSRIL 39
Cdd:cd15207  208 AQAAVSKKKVRVIKMLIVVVVLFALSWLPLHTVTML 243

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.

                         10        20        30
                 ....*....|....*....|....*....|....
gi 763708771  10 KQRREVAKTVFCLVLVFALCWLPLHLSRILKLTI 43
Cdd:cd14970  208 RARRKVTRLVLVVVAVFVVCWLPFHVFQIVRLLI 241

invertebrate neuropeptide receptor-like, member of the class A family of seven-transmembrane G protein-coupled receptors; This subgroup includes putative neuropeptide receptor found in invertebrates, which is a member of class A of 7-transmembrane G protein-coupled receptors. This orphan receptor shares a significant amino acid sequence identity with the neurokinin 1 receptor (NK1R). The endogenous ligand for NK1R is substance P, an 11-amino acid peptide that functions as a vasodilator and neurotransmitter and is released from the autonomic sensory nerve fibers.

                         10        20        30
                 ....*....|....*....|....*....|..
gi 763708771   8 HLKQRREVAKTVFCLVLVFALCWLPLHLSRIL 39
Cdd:cd15391  210 QIKSKRKVIKMLVFVVLMFGICWLPLHLFNLV 241

orexin receptors, member of the class A family of seven-transmembrane G protein-coupled receptors; 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. Thus, activation of OX1R or OX2R will activate phospholipase activity and the phosphatidylinositol and calcium signaling pathways. Additionally, OX2R activation can also lead to inhibition of adenylate cyclase.

                         10        20        30
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gi 763708771   9 LKQRREVAKTVFCLVLVFALCWLPLHLSRILK 40
Cdd:cd15208  226 LRSRRKTAKMLIVVVIMFAICYLPVHLLNILR 257

bombesin receptor subtype 3, member of the class A family of seven-transmembrane G protein-coupled receptors; BRS-3 is classified as an orphan receptor and belongs to the bombesin subfamily of G-protein coupled receptors, whose members also include neuromedin B receptor (NMBR) and gastrin-releasing peptide receptor (GRPR). Bombesin is a tetradecapeptide, originally isolated from frog skin. Mammalian bombesin-related peptides are widely distributed in the gastrointestinal and central nervous systems. The bombesin family receptors couple primarily to the G proteins of G(q/11) family. BRS-3 interacts with known naturally-occurring bombesin-related peptides with low affinity; however, no endogenous high-affinity ligand to the receptor has been identified. BRS-3 is suggested to play a role in sperm cell division and maturation.

                         10        20
                 ....*....|....*....|....*...
gi 763708771   8 HLKQRREVAKTVFCLVLVFALCWLPLHL 35
Cdd:cd15123  215 QIESRKRVAKTVLVLVALFAFCWLPNHI 242

gastrin-releasing peptide receptor, member of the class A family of seven-transmembrane G protein-coupled receptors; The gastrin-releasing peptide receptor (GRPR) is a G-protein coupled receptor whose endogenous ligand is gastrin releasing peptide. GRP shares high sequence homology with the neuropeptide neuromedin B in the C-terminal region. This receptor is high glycosylated and couples to a pertussis-toxin-insensitive G protein of the family of Gq/11, which leads to the activation of phospholipase C. Gastrin-releasing peptide (GRP) is a potent mitogen for neoplastic tissues and involved in regulating multiple functions of the gastrointestinal and central nervous systems. These include the release of gastrointestinal hormones, the contraction of smooth muscle cells, and the proliferation of epithelial cells. GRPR belongs to the bombesin subfamily of G-protein coupled receptors, whose members also include neuromedin B receptor (NMBR) and bombesin receptor subtype 3 (BRS-3). Bombesin is a tetradecapeptide, originally isolated from frog skin.

                         10        20        30        40
                 ....*....|....*....|....*....|....*....|.
gi 763708771   8 HLKQRREVAKTVFCLVLVFALCWLPLHLSRILKLTIYDEKD 48
Cdd:cd15124  215 QIESRKRLAKTVLVFVGLFAFCWLPNHIIYLYRSYHYSEVD 255

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.

                         10        20        30
                 ....*....|....*....|....*....|....*...
gi 763708771   6 SDHLKQRREVAKTVFCLVLVFALCWLPLHLSRILKLTI 43
Cdd:cd15088  201 SHGSSRTKRVTKMVILIVVVFIVCWLPFHVVQLVNLAM 238

tachykinin receptor and closely related proteins, member of the class A family of seven-transmembrane G protein-coupled receptors; This subfamily includes G-protein coupled receptors for a variety of neuropeptides of the tachykinin (TK) family as well as closely related receptors. The tachykinins are widely distributed throughout the mammalian central and peripheral nervous systems and act as excitatory transmitters on neurons and cells in the gastrointestinal tract. The TKs are characterized by a common five-amino acid C-terminal sequence, Phe-X-Gly-Leu-Met-NH2, where X is a hydrophobic residue. The three major mammalian tachykinins are substance P (SP), neurokinin A (NKA), and neurokinin B (NKB). The physiological actions of tachykinins are mediated through three types of receptors: neurokinin receptor type 1 (NK1R), NK2R, and NK3R. SP is a high-affinity endogenous ligand for NK1R, which interacts with the Gq protein and activates phospholipase C, leading to elevation of intracellular calcium. NK2R is a high-affinity receptor for NKA, the tachykinin neuropeptide substance K. SP and NKA are found in the enteric nervous system and mediate in the regulation of gastrointestinal motility, secretion, vascular permeability, and pain perception. NK3R is activated by its high-affinity ligand, NKB, which is primarily involved in the central nervous system and plays a critical role in the regulation of gonadotropin hormone release and the onset of puberty.

                         10        20        30
                 ....*....|....*....|....*....|..
gi 763708771   8 HLKQRREVAKTVFCLVLVFALCWLPLHLSRIL 39
Cdd:cd14992  214 RLKCKRRVIKMLVCVVVLFVICWLPFHLFFLL 245

tachykinin receptors and related receptors, member of the class A family of seven-transmembrane G protein-coupled receptors; This group includes the neurokinin/tachykinin receptors and its closely related receptors such as orphan GPR83 and leucokinin-like peptide receptor. The tachykinins are widely distributed throughout the mammalian central and peripheral nervous systems and act as excitatory transmitters on neurons and cells in the gastrointestinal tract. The TKs are characterized by a common five-amino acid C-terminal sequence, Phe-X-Gly-Leu-Met-NH2, where X is a hydrophobic residue. The three major mammalian tachykinins are substance P (SP), neurokinin A (NKA), and neurokinin B (NKB). The physiological actions of tachykinins are mediated through three types of receptors: neurokinin receptor type 1 (NK1R), NK2R, and NK3R. SP is a high-affinity endogenous ligand for NK1R, which interacts with the Gq protein and activates phospholipase C, leading to elevation of intracellular calcium. NK2R is a high-affinity receptor for NKA, the tachykinin neuropeptide substance K. SP and NKA are found in the enteric nervous system and mediate in the regulation of gastrointestinal motility, secretion, vascular permeability, and pain perception. NK3R is activated by its high-affinity ligand, NKB, which is primarily involved in the central nervous system and plays a critical role in the regulation of gonadotropin hormone release and the onset of puberty.

                         10        20        30
                 ....*....|....*....|....*....|.
gi 763708771   9 LKQRREVAKTVFCLVLVFALCWLPLHLSRIL 39
Cdd:cd15202  213 RRKKKKVIKMLMVVVVLFALCWLPFNIYVLL 243

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.

                          10        20        30        40
                  ....*....|....*....|....*....|....*....|.
gi 763708771   10 KQRREVAKTVFCLVLVFALCWLPLHLSRILKLTIYDEKDPN 50
Cdd:pfam00001 192 QRRRKALKTLAVVVVVFILCWLPYHIVNLLDSLALDCELSR 232

histamine receptor subtypes H3R and H4R, member of the class A family of seven-transmembrane G protein-coupled receptors; This group includes histamine subtypes H3R and H4R, members of the histamine receptor family, which belong to the class A of GPCRs. Histamine plays a key role as chemical mediator and neurotransmitter in various physiological and pathophysiological processes in the central and peripheral nervous system. Histamine exerts its functions by binding to four different G protein-coupled receptors (H1-H4). The H3 and H4 receptors couple to the G(i)-proteins, which leading to the inhibition of cAMP formation. The H3R receptor functions as a presynaptic autoreceptors controlling histamine release and synthesis. The H4R plays an important role in histamine-mediated chemotaxis in mast cells and eosinophils. 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.

                         10        20        30        40
                 ....*....|....*....|....*....|....*....|....
gi 763708771   7 DHLKQRREVAKTVFCLVLVFALCWLPLHLSRILkLTIYDEKDPN 50
Cdd:cd15048  221 VKLRRDRKAAKSLAILVLVFLICWAPYTILTII-RSFCSGSCVD 263

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.

                         10        20
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gi 763708771   9 LKQRREVAKTVFCLVLVFALCWLPLHL 35
Cdd:cd14968  212 LQKEVKAAKSLAIILFLFALCWLPLHI 238

galanin receptor and related proteins, member of the class A family of seven-transmembrane G protein-coupled receptors; This subfamily includes G-protein coupled galanin receptors, kisspeptin receptor and allatostatin-A receptor (AstA-R) in insects. These receptors, which are members of the class A of seven transmembrane GPCRs, share a high degree of sequence homology among themselves. The galanin receptors bind galanin, a neuropeptide that is widely expressed in the brain, peripheral tissues, and endocrine glands. Galanin is implicated in numerous neurological and psychiatric diseases including Alzheimer's disease, eating disorders, and epilepsy, among many others. KiSS1-derived peptide receptor (also known as GPR54 or kisspeptin receptor) binds the peptide hormone kisspeptin (metastin), which encoded by the metastasis suppressor gene (KISS1) expressed in various endocrine and reproductive tissues. AstA-R is a G-protein coupled receptor that binds allatostatin A. Three distinct types of allatostatin have been identified in the insects and crustaceans: AstA, AstB, and AstC. They both inhibit the biosynthesis of juvenile hormone and exert an inhibitory influence on food intake. Therefore, allatostatins are considered as potential targets for insect control.

                         10        20
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gi 763708771  12 RREVAKTVFCLVLVFALCWLPLHL 35
Cdd:cd14971  209 KRKVTRLVLVVVVLFAACWGPIHA 232

somatostatin receptor type 5, 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. SSTR5 is coupled to inward rectifying K channels and phospholipase C, and plays critical roles in growth hormone and insulin secretion. SSTR5 acts as a negative regulator of PDX-1 (pancreatic and duodenal homeobox-1) expression, which is a conserved homeodomain-containing beta cell-specific transcription factor essentially involved in pancreatic development, among many other functions.

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gi 763708771   1 VQIALSDHLKQRREVAKTVFCLVLVFALCWLPLHLSRILKLTIYDEKDP 49
Cdd:cd15974  194 LRVGSTKRRKSERKVTRMVVIIVVVFVFCWLPFYMLNIVNLIVILPEEP 242

CXC chemokine receptor types 1 and 2, member of the class A family of seven-transmembrane G protein-coupled receptors; CXCR1 and CXCR2 are closely related chemotactic receptors for a group of CXC chemokines distinguished by the presence of the amino acid motif ELR immediately adjacent to their CXC motif. Expression of CXCR1 and CXCR2 is strictly controlled in neutrophils by external stimuli such as lipopolysaccharide (LPS), tumor necrosis factor (TNF)-alpha, Toll-like receptor agonists, and nitric oxide. CXCL8 (formerly known as interleukin-8) binds with high-affinity and activates both receptors. CXCR1 also binds CXCL7 (neutrophil-activating protein-2), whereas CXCR2 non-selectively binds to all seven ELR-positive chemokines (CXCL1-7). 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.

                         10        20        30
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gi 763708771   5 LSDHLKQRREVAKTVFCLVLVFALCWLPLHLS 36
Cdd:cd15178  193 LQTRSFQKHRAMRVIFAVVLAFLLCWLPYNVT 224

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 763708771   9 LKQRREVAKTVFCLVLVFALCWLPLHLSRIL 39
Cdd:cd15203  216 LRRKRRTNRLLIAMVVVFAVCWLPLNLFNLL 246

growth hormone secretagogue receptor, member of the class A family of seven-transmembrane G protein-coupled receptors; Growth hormone secretagogue receptor, GHSR, is also known as GH-releasing peptide receptor (GHRP) or Ghrelin receptor. Ghrelin, the endogenous ligand for GHSR, is an acylated 28-amino acid peptide hormone produced by ghrelin cells in the gastrointestinal tract. Ghrelin, also called hunger hormone, is involved in the regulation of growth hormone release, appetite and feeding, gut motility, lipid and glucose metabolism, and energy balance. It also plays a role in the cardiovascular, immune, and reproductive systems. GHSR couples to G-alpha-11 proteins. Both ghrelin and GHSR are expressed in a wide range of cancer tissues. Recent studies suggested that ghrelin may play a role in processes associated with cancer progression, including cell proliferation, metastasis, apoptosis, and angiogenesis.

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gi 763708771  10 KQRREVAKTVFCLVLVFALCWLPLHLSRIL 39
Cdd:cd15131  213 KNNRQTVKMLAVVVFAFVLCWLPFHVGRYL 242

G protein-coupled chemokine receptor-like protein; Provisional

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gi 763708771  10 KQRREVAKTVFCLVLVFALCWLPLHLSRIL 39
Cdd:PHA03087 237 KKNKKAIKLVLIIVILFVIFWLPFNVSVFV 266

somatostatin receptors, 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. They share common signaling cascades such as inhibition of adenylyl cyclase, activation of phosphotyrosine phosphatase activity, and G-protein-dependent regulation of MAPKs.

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gi 763708771  10 KQRREVAKTVFCLVLVFALCWLPLHLSRILKLTIYDEKDP 49
Cdd:cd15093  206 RSERKVTRMVVMVVVVFVICWLPFYVLQLVNVFVQLPETP 245

P2Y purinoceptors 1, 2, 4, 6, 11 and similar proteins, member of the class A family of seven-transmembrane G protein-coupled receptors; The P2Y receptor family is composed of eight subtypes, which are activated by naturally occurring extracellular nucleotides such as ATP, ADP, UTP, UDP, and UDP-glucose. These eight receptors are ubiquitous in human tissues and can be further classified into two subfamilies based on sequence homology and second messenger coupling: a subfamily of five P2Y1-like receptors (P2Y1, P2Y2, P2Y4, P2Y6, and P2Y11Rs) that are coupled to G(q) protein to activate phospholipase C (PLC) and a second subfamily of three P2Y12-like receptors (P2Y12, P2YR13, and P2Y14Rs) that are coupled to G(i) protein to inhibit adenylate cyclase. Several cloned subtypes, such as P2Y3, P2Y5, and P2Y7-10, are not functional mammalian nucleotide receptors. The native agonists for P2Y receptors are: ATP (P2Y2, P2Y12), ADP (P2Y1, P2Y12, and P2Y13), UTP (P2Y2, P2Y4), UDP (P2Y6, P2Y14), and UDP-glucose (P2Y14). This cluster only includes P2Y1-like receptors as well as other closely related orphan receptors, such as GPR91 (a succinate receptor) and GPR80/GPR99 (an alpha-ketoglutarate receptor).

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gi 763708771  11 QRREVAKTVFCLVLVFALCWLPLHLSRILKL 41
Cdd:cd15168  204 LRRKSIRLVIIVLALFAVCFLPFHVTRTINL 234