Cross references: Receptors in General Ligands Gq Protein
Glutamate Metabotropic Receptor GABA Metabotropic Receptor
Serotonin Metabotropic Receptor Acetylcholine Metabotropic Receptor
Neuropeptide Receptor Melatonin Receptor Arrestin & Rhodopsin Receptors
G protein-coupled receptor (Wiki)
"G protein-coupled receptors (GPCRs), also known as seven-transmembrane domain receptors, 7TM receptors, heptahelical receptors, serpentine receptor, and G protein-linked receptors (GPLR), comprise a large protein family of transmembrane receptors that sense molecules outside the cell and activate inside signal transduction pathways and, ultimately, cellular responses."
" The seven-transmembrane α-helix structure of a G-protein-coupled receptor."
"G protein-coupled receptors are found only in eukaryotes, including yeast, choanoflagellates, and animals. The ligands that bind and activate these receptors include light-sensitive compounds, odors, pheromones, hormones, and neurotransmitters, and vary in size from small molecules to peptides to large proteins."
"There are two principal signal transduction pathways involving the G-protein coupled receptors: the cAMP signal pathway and the Phosphatidylinositol signal pathway."
"The human genome encodes thousands of G protein-coupled receptors ..." and they "... are involved in a wide variety of physiological processes.
Some examples of their physiological roles include:
The ligands that bind and activate these receptors include light-sensitive compounds, odors, pheromones, hormones, and neurotransmitters, and vary in size from small molecules to peptides to large proteins." '
Functional Pairing of Class B1 Ligand-GPCR in Cephalochordate Provides Evidence of the Origin of PTH and PACAP/Glucagon Receptor Family.
" In summary, our data confirm the presence of PTH and PACAP/GLUC ligand-receptor pairs in amphioxus, demonstrating that functional homologs of vertebrate PTH and PACAP/glucagon GPCR subfamilies arose before the cephalochordate divergence from the ancestor of tunicates and vertebrates. "
G protein (Wiki)
"G proteins (guanine nucleotide-binding proteins) are a family of proteins involved in transmitting chemical signals outside the cell, and causing changes inside the cell. They communicate signals from many hormones, neurotransmitters, and other signaling factors. "
"G protein-coupled receptors are receptors that pass through the cell membrane. Signal molecules bind to the receptor outside the cell. The receptor inside the cell activates a G protein. The G protein activates a cascade of further compounds, and finally causes a change downstream in the cell. G protein complexes bind to phosphate groups. They function as molecular switches.
When they are attached to a complex with three phosphate groups (guanosine triphosphate [GTP]), they turn on."
"When they are attached to a complex with only two phosphate groups (guanosine diphosphate [GDP]), they turn off."
These hydrophilic (and mostly large) hormone molecules bind to receptors on the surface of "target" cells; that is, cells able to respond to the presence of the hormone. These receptors are transmembrane proteins. Binding of the hormone to its receptor initiates a sequence of intracellular signals that may
guanine nucleotides GDP and GTP. They are heterotrimers (i.e., made of three different subunits) associated with
This type stimulates (s = "stimulatory") adenylyl cyclase. It is the one depicted here. It is associated with the receptors for many hormones such as:
This inhibits (i = "inhibitory") adenylyl cyclase lowering the level of cAMP in the cell. Gai is activated by the receptor for somatostatin.
7 February 2007