Of G-coupled proteins

G-coupled proteins transduce a message from the external environment to the interior of the cell through a series of coupled molecular events. These have been described in chapter 2. 

Effect of lithium on the IP3 and DAG second-messenger system. The schematic diagram shows the synaptic membrane of a neuron. (PIP2, phosphatidylinositol-4,5-bisphosphate PLC, phospholipase-C G, coupling protein EFFECTS, activation of protein kinase C, mobilization of intracellular Ca2+, etc.) Lithium, by inhibiting the recycling of inositol substrates, may cause... 

G-coupled protein, on the surface of white blood cells. After this interaction has commenced it sets off a conformational change that reveals another binding site on the virus to strengthen the virus-cell affinity. Once the virus-membrane interaction is cemented in this way it paves the way for the virus to transfer its genetic material into the host cell. 

In spite of the success and wide use, 2D gel is a relatively slow, labor-intensive and cumbersome technique, even with the availability of prefabricated strips for the first dimension (isoelectric focusing) and the pre-cast gels used in the second dimension. Another limitation is its inability to resolve lower abundance (less stable) proteins, membrane proteins, highly acidic or basic proteins, very large or small proteins, and hydrophobic proteins like G-coupled protein receptors with several transmembrane regions. 

A new histamine receptor, the H4 subtype, was fint reported in 2000 and characterized as a 390-amino acid. G,-coupled protein with 40% identity to the H3 receptor. " This new receptor exhibits a very restricted localization expression is primarily found in intestinal tissue, spleen, thymus, and immune active cells, such as T cells, neutrophils, and eosinophils, which sugge.sts an important role for Hi receptors in the regulation of immune function. 

Fig. 2 A phylogenetic tree of the animals, in which the evolution of odorant receptor (OR) genes were explored. In nematodes, Ciona and vertebrates, OR genes belong to the family of seven-transmembrane G-coupled-protein receptors (GPCR). An ancestor of insects possessing a unique OR gene family appeared after branching from the arthropod ancestor. Thus, the origin of insect OR genes is likely to have arisen independently of the GPCR family...

The cannabinoid receptor belongs to a large family of receptor proteins that span the cell membrane, known as G-coupled protein receptors. Membrane receptor proteins are illustrated in Figure 24.4. 

G-coupled protein receptors are involved in many diseases. It is estimated that nearly one-half of prescription drugs target GCPRs, in the treatment of cancer, cardiac malfunction, inflammation, pain, and disorders of the central nervous system. 

Signal transduction is initiated by the binding of a G-coupled protein receptor (GCPR) to the ligand on the exterior of the cell. Interactions with a nearby G protein inside the cell results in the exchange of bound GDP to GTP and in the release of one of its subunits in a GTP-bound form that activates an ion... 

G-coupled protein receptors A large family of protein receptors that function as transmembrane molecular switches to regulate many physiological processes. 

There is an increased emphasis on bioorganic chemistry, with new coverage of glycobiology, liposomes, G-coupled protein receptors, recombinant DNA technology, and other topics. 

Detailed characterization of opioid receptors began in 1992 with the identification and cloning of the OPl (delta) receptor, followed by subsequent identification and cloning of OP2 (kappa) and OP3 (mu) receptors. All of these receptors are G-coupled proteins that have seven transmembrane domains and share 60% of structural homology. In 1994, a new receptor subtype was identified and was originally given the name opioid receptor like-1 (ORL-1). This subtype has typical opioid receptor characteristics, such as a G-coupled... 

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