Beta-gamma complex
Encyclopedia
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The beta-gamma complex is composed of the heterotrimeric G protein
s Gβ (beta subunit) and Gγ (gamma subunit) that are closely bound to one another.
Upon activation of a G-protein coupled receptor, the Gβγ complex is released from the Gα subunit
, allowing the Gα subunit to function as a messenger in signal transduction
.
s directly.
Examples of Gβγ complex functions include:
GNB1L and GNB2L1 are not considered to be classical G protein beta subunits, as they do not make part of the beta/gamma protein complex and only show sequence similarities with the true Gβ proteins (ref NCBI GeneID: 54584, GeneID: 10399).
The beta-gamma complex is composed of the heterotrimeric G protein
Heterotrimeric G protein
"G protein" usually refers to the membrane-associated heterotrimeric G proteins, sometimes referred to as the "large" G proteins. These proteins are activated by G protein-coupled receptors and are made up of alpha , beta and gamma subunits, the latter two referred to as the beta-gamma...
s Gβ (beta subunit) and Gγ (gamma subunit) that are closely bound to one another.
Upon activation of a G-protein coupled receptor, the Gβγ complex is released from the Gα subunit
G alpha subunit
Guanine nucleotide binding proteins are membrane-associated, heterotrimeric proteins composed of three subunits: alpha , beta and gamma . G proteins and their receptors form one of the most prevalent signalling systems in mammalian cells, regulating systems as diverse as sensory perception, cell...
, allowing the Gα subunit to function as a messenger in signal transduction
Signal transduction
Signal transduction occurs when an extracellular signaling molecule activates a cell surface receptor. In turn, this receptor alters intracellular molecules creating a response...
.
Function
The normal role of the beta-gamma complex is inhibition of the Gα subunit. However, the free Gβγ complex can act as a signaling molecule itself, by activating other second messengers or by gating ion channelIon channel
Ion channels are pore-forming proteins that help establish and control the small voltage gradient across the plasma membrane of cells by allowing the flow of ions down their electrochemical gradient. They are present in the membranes that surround all biological cells...
s directly.
Examples of Gβγ complex functions include:
- Activation of phospholipase A2Phospholipase A2Phospholipases A2 are enzymes that release fatty acids from the second carbon group of glycerol. This particular phospholipase specifically recognizes the sn-2 acyl bond of phospholipids and catalytically hydrolyzes the bond releasing arachidonic acid and lysophospholipids...
when bound to histamineHistamineHistamine is an organic nitrogen compound involved in local immune responses as well as regulating physiological function in the gut and acting as a neurotransmitter. Histamine triggers the inflammatory response. As part of an immune response to foreign pathogens, histamine is produced by...
receptors - Direct opening of G-protein coupled inward rectifying potassium channelsInward-rectifier potassium ion channelInwardly rectifying potassium channels are a specific subset of potassium selective ion channels. To date, seven subfamilies have been identified in various mammalian cell types...
(GIRKs) when bound to muscarinicMuscarineMuscarine, L--muscarine, or muscarin is a natural product found in certain mushrooms, particularly in Inocybe and Clitocybe species, such as the deadly C. dealbata. Mushrooms in the genera Entoloma and Mycena have also been found to contain levels of muscarine which can be dangerous if ingested...
acetylcholineAcetylcholineThe chemical compound acetylcholine is a neurotransmitter in both the peripheral nervous system and central nervous system in many organisms including humans...
receptors - Activation L-type calcium channels, as in H3 receptor pharmacology.
- Initiation of the phospholipase C pathway by activating phospholipase C, as a minor mechanism of growth hormone releasing hormoneGrowth hormone releasing hormoneGrowth-hormone-releasing hormone , also known as growth-hormone-releasing factor , somatoliberin or somatocrinin, is a releasing hormone for growth hormone...
releasing growth hormoneGrowth hormoneGrowth hormone is a peptide hormone that stimulates growth, cell reproduction and regeneration in humans and other animals. Growth hormone is a 191-amino acid, single-chain polypeptide that is synthesized, stored, and secreted by the somatotroph cells within the lateral wings of the anterior...
.
Genes
- Gβ genes: GNB1GNB1Guanine nucleotide-binding protein G/G/G subunit beta-1 is a protein that in humans is encoded by the GNB1 gene.-Further reading:...
, GNB2GNB2Guanine nucleotide-binding protein G/G/G subunit beta-2 is a protein that in humans is encoded by the GNB2 gene.-Further reading:...
, GNB3GNB3Guanine nucleotide-binding protein G/G/G subunit beta-3 is a protein that in humans is encoded by the GNB3 gene.-Further reading:...
, GNB4GNB4Guanine nucleotide-binding protein subunit beta-4 is a protein that in humans is encoded by the GNB4 gene.-Further reading:...
, GNB5GNB5Guanine nucleotide-binding protein subunit beta-5 is a protein that in humans is encoded by the GNB5 gene.-Interactions:GNB5 has been shown to interact with GNG13, GNG7 and RGS7.-Further reading:...
, , GNB2L1GNB2L1Guanine nucleotide-binding protein subunit beta-2-like 1 is a protein that in humans is encoded by the GNB2L1 gene.-Interactions:GNB2L1 has been shown to interact with PDE4D, STAT1, Tyrosine kinase 2, Src, Androgen receptor, AGTRAP, Janus kinase 1, FYN, Cyclin A1, IFNAR2, PRKCE, P73, RAS p21...
GNB1L and GNB2L1 are not considered to be classical G protein beta subunits, as they do not make part of the beta/gamma protein complex and only show sequence similarities with the true Gβ proteins (ref NCBI GeneID: 54584, GeneID: 10399).
- Gγ genes: GNGT1GNGT1Guanine nucleotide-binding protein G subunit gamma-T1 is a protein that in humans is encoded by the GNGT1 gene.-Further reading:...
, GNGT2GNGT2Guanine nucleotide-binding protein G/G/G subunit gamma-T2 is a protein that in humans is encoded by the GNGT2 gene.-Further reading:...
, GNG2GNG2Guanine nucleotide-binding protein G/G/G subunit gamma-2 is a protein that in humans is encoded by the GNG2 gene.- Interactive pathway map :...
, GNG3GNG3Guanine nucleotide-binding protein G/G/G subunit gamma-3 is a protein that in humans is encoded by the GNG3 gene.-Further reading:...
, GNG4GNG4Guanine nucleotide-binding protein G/G/G subunit gamma-4 is a protein that in humans is encoded by the GNG4 gene.-Further reading:...
, GNG5GNG5Guanine nucleotide-binding protein G/G/G subunit gamma-5 is a protein that in humans is encoded by the GNG5 gene.-Further reading:...
, GNG7GNG7Guanine nucleotide-binding protein G/G/G subunit gamma-7 is a protein that in humans is encoded by the GNG7 gene.-Further reading:...
, GNG8, GNG10, GNG11GNG11Guanine nucleotide-binding protein G/G/G subunit gamma-11 is a protein that in humans is encoded by the GNG11 gene.-Further reading:...
, GNG12GNG12Guanine nucleotide-binding protein G/G/G subunit gamma-12 is a protein that in humans is encoded by the GNG12 gene.-Further reading:...
, GNG13GNG13Guanine nucleotide-binding protein G/G/G subunit gamma-13 is a protein that in humans is encoded by the GNG13 gene.-Further reading:...