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14-September-2008 18:02:45 - receptor Transmembrane receptors are integral membrane proteins, which reside and operate typically within a cell's plasma membrane, but also in the membranes of some subcellular compartments and organelles. Binding to a signalling molecule or sometimes to a pair of such molecules on one side of the membrane, transmembrane receptors initiate a response on the other side. In this way they play a unique and important role in cellular communications and signal transduction. Many transmembrane receptors are composed of two or more protein subunits which operate collectively and may dissociate when ligands bind, fall off, or at another stage of their activation cycles. They are often classified based on their molecular structure, or because the structure is unknown in any detail for all but a few receptors, based on their hypothesized and sometimes experimentally verified membrane topology. The polypeptide chains of the simplest are predicted to cross the lipid bilayer only once, while others cross as many as seven times the so-called G-protein coupled receptors. Contents 1 Domains 1.1 Extracellular domain 1.2 Transmembrane domain 1.3 Intracellular domain 2 Regulation of receptor activity 3 Examples of transmembrane receptors 4 See also 5 External links Domains Like any integral membrane protein, a transmembrane receptor may be subdivided into three parts or domains. Image:transmembrane receptor.png E=extracellular space; I=intracellular space; P=plasma membrane Extracellular domain The extracellular domain is the part of the receptor that sticks out of the membrane on the outside of the cell or organelle. If the polypeptide chain of the receptor crosses the bilayer several times, the external domain can comprise several loops sticking out of the membrane. By definition, a receptor's main function is to recognize and respond to a specific ligand, for example, a neurotransmitter or hormone although certain receptors respond also to changes in transmembrane potential, and in many receptors these ligands bind to the extracellular domain. Transmembrane domain In the majority of receptors for which structural evidence exists, transmembrane alpha helices make up most of the transmembrane domain. In certain receptors, such as the nicotinic acetylcholine receptor, the transmembrane domain forms a protein-lined pore through the membrane, or ion channel. Upon activation of an extracellular domain by binding of the appropriate ligand, the pore becomes accessible to ions, which then pass through. In other receptors, the transmembrane domains are presumed to undergo a conformational change upon binding, which exerts an effect intracellularly. In some receptors, such as members of the 7TM superfamily, the transmembrane domain may contain the ligand binding pocket evidence for this and for much of what else is known about this class of receptors is based in part on studies of bacteriorhodopsin, the detailed structure of which has been determined by crystallography. Intracellular domain The intracellular or cytoplasmic domain of the receptor interacts with the interior of the cell or organelle, relaying the signal. There are two fundamentally different ways for this interaction: The intracellular domain communicates via specific protein-protein-interactions with effector proteins, which in turn send the signal along a signal chain to its destination. With enzyme-linked receptors, the intracellular domain has enzymatic activity. Often, this is a tyrosine kinase activity. The enzymatic activity can also be located on an enzyme associated with the intracellular domain. Regulation of receptor activity There are several ways for the cell to regulate the activity of a transmembrane receptor. Most of them work through the intracellular domain. The most important ways are phosphorylation and internalization see ubiquitin. Examples of transmembrane receptors G-protein coupled receptors - Adrenergic receptor, Olfactory receptors, Receptor tyrosine kinases - Epidermal growth factor receptor, Insulin Receptor, Fibroblast growth factor receptors, High affinity neurotrophin receptors, and Eph Receptors Integrins Low Affinity Nerve Growth Factor Receptor NMDA receptor Several Immune receptors Toll-like receptor T cell receptor CD28 See also Signal transduction G protein Second messenger Neuromodulators External links IUPHAR GPCR Database MeSH Cell+Surface+Receptors v d e Cell signaling Key concepts Signal transduction - Apoptosis - Second messenger system Ca2+ signaling, Lipid signaling Processes Paracrine - Autocrine - Juxtacrine - Neurotransmitters - Endocrine Neuroendocrine Signaling pathways Hedgehog signaling pathway - Wnt signaling pathway - TGF beta signaling pathway - MAPK/ERK pathway - Notch signaling pathway - JAK-STAT signaling pathway - cAMP dependent pathway - Akt/PKB signaling pathway Agents Receptor ligands Hormones - Neurotransmitters - Cytokines - Growth factors Receptor Transmembrane - Intracellular Transcription factor General - Preinitiation complex - TFIID, TFIIH Other Adaptor protein v d e Transmembrane receptor: G protein-coupled receptors Class A: Rhodopsin like Adrenergic α1 A, B, D, α2 A, B, C, β1, β2, β3 Eicosanoid CysLT 1, 2, LTB4 1, 2, FPRL1, OXE, Prostaglandin DP, EP 1, 2, 3, 4, PGF, Prostacyclin, Thromboxane Neuropeptide B/W 1, 2, FF 1, 2, S, Y 1, 2, 4, 5 Orphan GPR 1, 3, 4, 6, 12, 15, 17, 18, 19, 20, 21, 22, 23, 25, 26, 27, 31, 32, 33, 34, 35, 37, 39, 42, 44, 45, 50, 52, 55, 61, 62, 63, 65, 68, 75, 77, 78, 79, 82, 83, 84, 85, 87, 88, 92, 101, 103, 119, 120, 132, 135, 139, 141, 142, 146, 148, 149, 150, 151, 152, 153, 160, 161, 162, 171, 172, 173, 174, 176, 177, 182 Purinergics Adenosine A1, A2a, A2b, A3, P2Y, 1, 2, 4, 5, 6, 8, 9, 10, 11, 12, 13, 14 Serotonin all but 5-HT3 5-HT1 A, B, D, E, F, 5-HT2 A, B, C, 5-HT 4, 5A, 6, 7 Other Acetylcholine M1, M2, M3, M4, M5 - Adrenomedullin - Anaphylatoxin C3a, C5a - Angiotensin 1, 2 - Apelin - Bile acid - Bombesin BRS3, GRPR, NMBR - Bradykinin B1, B2 - Cannabinoid CB1, CB2 - Chemokine - Cholecystokinin A, B - Dopamine D1, D2, D3, D4, D5 - EBI2 - Endothelin A, B - Estrogen - Formyl peptide 1, L1, L2 - Free fatty acid 1, 2, 3, 4 - FSH - Galanin 1, 2, 3 - Gonadotropin-releasing hormone 1, 2 - Ghrelin - Histamine H1, H2, H3, H4 - Kisspeptin - Luteinizing hormone/choriogonadotropin - Lysophospholipid 1, 2, 3, 4, 5, 6, 7, 8 - MAS 1, 1L, D, E, F, G, X1, X2, X3, X4 - Melanocortin 1, 2, 3, 4, 5 - MCHR 1, 2 - Melatonin 1A, 1B- Motilin - neuromedin B, U 1, 2 - Neurotensin 1, 2 - Opioid Delta, Kappa, Mu, Nociceptin, but not Sigma - Olfactory - Opsin 3, 4, 5, 1LW, 1MW, 1SW, RGR, RRH - Orexin 1, 2 - Oxytocin - Oxoglutarate - PAF - Prokineticin 1, 2 - Prolactin-releasing peptide - Protease-activated 1, 2, 3, 4 - Relaxin 1, 2, 3, 4 - Somatostatin 1, 2, 3, 4, 5 - SREB - Succinate - TAAR 1, 2, 3, 5, 6, 8, 9 - Tachykinin 1, 2, 3 - Thyrotropin - Thyrotropin-releasing hormone - Urotensin-II - Vasopressin 1A, 1B, 2 Class B: Secretin like Brain-specific angiogenesis inhibitor 1, 2, 3 - Cadherin 1, 2, 3 - Calcitonin - CD97 - Corticotropin-releasing hormone 1, 2 - EMR 1, 2, 3 - Glucagon GR, GIPR, GLP1R, GLP2R - Growth hormone releasing hormone - PACAPR1- GPR 56, 64, 97, 98, 110, 111, 112, 113, 114, 115, 116, 123, 124, 125, 126, 128, 133, 143, 144, 157 - Latrophilin 1, 2, 3, ELTD1 - Parathyroid hormone 1, 2 - Secretin - Vasoactive intestinal peptide 1, 2 Class C: Metabotropic glutamate / pheromone Calcium-sensing receptor - GABA B 1, 2 - Glutamate receptor Metabotropic glutamate 1, 2, 3, 4, 5, 6, 7, 8 - GPRC6A - GPR 156, 158, 179 - RAIG 1, 2, 3, 4 - Taste receptors TAS1R 1, 2, 3 TAS2R 1, 3, 4, 5, 8, 9, 10, 12, 13, 14, 16, 38, 39, 40, 41, 43, 44, 45, 46, 47, 48, 49, 50 Frizzled / Smoothened Frizzled 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 - Smoothened v d e Transmembrane receptor, tyrosine kinase: receptor tyrosine kinases EC 2.7.10.1 I: EGF/ErbB HER2/neu - Her 3 - Her 4 II Insulin - IGF-1 III: PDGF A - B IV: FGF FGFR1 - FGFR2 - FGFR3 - FGFR4 V: VEGF 1 - 2 VII: TRK TrkA - TrkB - TrkC VIII: Eph A EPHA1, EPHA2, EPHA3, EPHA4, EPHA5, EPHA6, EPHA7, EPHA8, EPHA9, EPHA10 B EPHB1, B2, EPHB3, EPHB4, EPHB5, EPHB6 XI: Angiopoietin TIE1 - TIE2 Other XIV: RET - XVI: Related to receptor tyrosine kinase - XVII: MuSK v d e Transmembrane receptors: immune receptors Cytokine receptor Type I Interleukins 2, 3, 4, 5, 6, 7, 9, 11, 12, 13, 15, 21, 23, 27, CSF receptors EPO, GM-CSF, G-CSF, GH, prolactin, Oncostatin M,Leukemia inhibitory factor - common subunits Common gamma chain, common beta chain, CSF2RB Type II Interleukins 10, 20, 22, 28 - interferon -α/β, -γ Ig superfamily CSF1, C-kit, IL-1, IL-18 TNF CD27, CD30, CD40, CD120, Lymphotoxin β Chemokines IL-8 α, β, CCR1,CXCR4 Other IL-17, TGF-beta 1, 2 Pattern recognition/Toll-like TLR 1 - TLR 2 - TLR 3 - TLR 4 - TLR 5 - TLR 6 - TLR 7 - TLR 8 - TLR 9 - TLR 10 Fc receptor ε FcεRI, FcεRII γ FcγRI, FcγRII, FcγRIII, Neonatal α/μ FcαRI, Fcα/μR Lymphocyte homing receptor CD44 - L-selectin - integrin VLA-4, LFA-1 other Antigen receptor B-cell, T cell - Complement - Formyl peptide - Immunophilins - Integrin - Killer-cell immunoglobulin-like - Scavenger Retrieved from http://en..org/wiki/Transmembrane_receptor Categories: Cell signaling | Signal transduction | Transmembrane receptors | Receptor tyrosine kinases Views Article Discussion this page History Personal tools Log in / create account Navigation Main page Contents Featured content Current events Random article Search Go Search Interaction Community portal Recent changes Contact Donate to Help Toolbox What links here Related changes Upload file Special pages Printable version Permanent link Cite this page Languages Türkçe Deutsch Français Italiano Occitan This page was last modified on 22 June 2008, at 00:01
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So many of us do not eat a balanced diet, get enough sleep, have too much stress, or are impacted with toxins and pollutants. Drinking 2 ounces of MonaVie twice a day will help your body detoxify as well as build your immune system. Its the smartest thing you can do for yourself, so start today. Buying MonaVie through our company guarantees you support 7 days a week and, if you would like to share MonaVie with your family and friends we will guide you from start to finish.
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