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Information on EC 3.6.5.1 - heterotrimeric G-protein GTPase
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3.6.5.1 heterotrimeric G-protein GTPaseIUBMB Comments
This group comprises GTP-hydrolysing systems, where GTP and GDP alternate in binding. This group includes stimulatory and inhibitory G-proteins such as Gs, Gi, Go and Golf, targetting adenylate cyclase and/or K+ and Ca2+ channels; Gq stimulating phospholipase C; transducin activating cGMP phosphodiesterase; gustducin activating cAMP phosphodiesterase. Golf is instrumental in odour perception, transducin in vision and gustducin in taste recognition. At least 16 different alpha subunits (39-52 kDa), 5 beta subunits (36 kDa) and 12 gamma subunits (6-9 kDa) are known.
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Word Map
- 3.6.5.1
- guanine
- g-proteins
- toxin
- actin
- gdp
- cyclase
-
gtp-binding
- rhoa
- cytoskeleton
- retinal
- pertussis
- cdc42
- agonist
- rac1
- rhodopsin
-
adp-ribosylation
- photoreceptors
-
protein-coupled
- alpha-subunits
- galphas
- phospholipase
-
adenylyl
- camp
-
endocytosis
- microtubule
-
nucleotide-binding
- endosomes
- dynamin
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gdp-bound
- adenylate
- rgs
-
fission
- cholera
-
endocytic
-
gpcrs
-
ras-related
-
dominant-negative
- cytokine
-
phototransduction
- pigmentosa
- diphtheria
-
ribosylation
-
muscarinic
-
toxin-sensitive
- opsin
-
gtp-dependent
-
gppnhp
-
pleckstrin
-
dynamin-related
-
p21-activated
- medicine
- drug development
The expected taxonomic range for this enzyme is: Eukaryota, Bacteria, Archaea
Synonyms
gtpase, transducin, gs alpha, heterotrimeric g protein, galphaq, guanosine triphosphatase, elongation factor 2, heterotrimeric g-protein, rab1a, g alpha q, 
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SYNONYM 
ORGANISM
UNIPROT
COMMENTARY 
LITERATURE
EC 3.6.1.46
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formerly
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G12
G13
Galpha protein
GPA1
GTP phosphohydrolase
GTPase
guanosine 5'-triphosphatase
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guanosine triphosphatase
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heterotrimeric G protein
heterotrimeric G protein family
heterotrimeric G-protein
heterotrimeric G-protein GTPase
heterotrimeric GTPase
phosphatase, guanosine tri-
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ribosomal GTPase
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transducin
transducin GTPase
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GTP phosphohydrolase
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GTPase
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REACTION
REACTION DIAGRAM
COMMENTARY
ORGANISM
UNIPROT
LITERATURE
GTP + H2O = GDP + phosphate
binding and hydrolysis of GTP triggers reciprocal conformational changes within a switch region within the catalytic domain
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GTP + H2O = GDP + phosphate
in the classic paradigm of G-protein signaling, GDP-bound Galpha remains associated with the non-dissociable betagamma subunits and, in combination with a G-protein coupled receptor (GPCR), represents the inactive state of the signaling pathway. Signal perception by GPCR facilitates the exchange of GTP for bound GDP on Galpha. The GTP-bound Galpha dissociates from the Gbetagamma dimer and both entities can interact with specific downstream effectors to transduce the signal. Galpha is restored to its GDP-bound conformation by its own intrinsic GTPase activity which leads to its reassociation with the Gbetagamma dimer and GPCR. The switch-like signaling mechanism has two distinct regulatory steps: the rate of GDP-GTP exchange facilitated by a cognate GPCR, which involves GDP release and GTP binding; and the rate of GTP hydrolysis by the Galpha protein
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GTP + H2O = GDP + phosphate
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REACTION TYPE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
hydrolysis
hydrolysis of phosphoric ester
phosphorous acid anhydride hydrolysis
phosphorous acid anhydride hydrolysis
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SYSTEMATIC NAME
IUBMB Comments
GTP phosphohydrolase (signalling)
This group comprises GTP-hydrolysing systems, where GTP and GDP alternate in binding. This group includes stimulatory and inhibitory G-proteins such as Gs, Gi, Go and Golf, targetting adenylate cyclase and/or K+ and Ca2+ channels; Gq stimulating phospholipase C; transducin activating cGMP phosphodiesterase; gustducin activating cAMP phosphodiesterase. Golf is instrumental in odour perception, transducin in vision and gustducin in taste recognition. At least 16 different alpha subunits (39-52 kDa), 5 beta subunits (36 kDa) and 12 gamma subunits (6-9 kDa) are known.
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CAS REGISTRY NUMBER
COMMENTARY
9059-32-9
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SUBSTRATE
PRODUCT
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate)
(Substrate)
LITERATURE
(Substrate)
(Substrate)
COMMENTARY
(Product)
(Product)
LITERATURE
(Product)
(Product)
Reversibility
r=reversible
ir=irreversible
?=not specified
r=reversible
ir=irreversible
?=not specified
GTP + H2O
GDP + phosphate
-
activates phosphoinositide-specific phospholipase C in the presence of aluminium fluoride
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?
GTP + H2O
GDP + phosphate
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conformational change induced by the exchange of GDP for GTP in transducin and gustducin
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?
GTP + H2O
GDP + phosphate
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Gq/11 is the physiological regulator of phospholipase C-beta1
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-
?
GTP + H2O
GDP + phosphate
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specific GTP/GDP-binding and GTP-hydrolysis activity of recombinant CaGalpha1 protein, no binding of ATP or ADP
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-
?
GTP + H2O
GDP + phosphate
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usage of fluorescence-labeled 4,4-difluoro-4-bora-3alpha,4alpha-diaza-s-indacene-GTP substrate for assays
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-
?
GTP + H2O
GDP + phosphate
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intrinsic GTPase activity of transducin controls inactivation of the effector enzyme, cGMP phosphodiesterase during turnoff of the visual signal
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?
GTP + H2O
GDP + phosphate
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cycle of G protein activation and deactivation that transmits a signal from receptor to effector: when GDP is bound the alpha subunit associated with the betagamma subunit to form an inactive heterotrimer that binds to the receptor. Both alpha and betagamma subunits can bind to the receptor. When a chemical or physical signal stimulates the receptor, the receptor becomes activated and changes its conformation. The GDP-ligated alpha-subunit responds with a conformational change that decreases GDP affinity, so that GDP is released. Leaving GDP is replaced by GTP. Once ATP is bound, the alpha subunit assumes its activated conformation and dissociates both from the receptor and from betagamma. The activated state lasts until the GTP is hydrolyzed to GDP by the intrinsic GTPase activity of the alpha-subunit. Once GTP is cleaved to GDP, the alpha and betagamma subunits reassociate, become inactive, and return to the receptor. The free alpha and betagamma subunits each activate target effectors. Galphas and Galphaolf, stimulate adenylyl cyclase and regulate Ca2+ channels. Galphai-1, Galphai-2, Galphai-3, Galphao, Galphat-1, Galphat-2, Galphagust and Galphaz inhibit adenylyl cyclase, regulate K+ and Ca2+ channels, and activate cGMP phosphodiesterase. Galphaq, Galpha11, Galpha14, Galppha15 and Galpha16 activate phospholipase C. Galpha12 and Galpha13 regulate Na/K+ exchange. The betagamma subunit is a positive regulator of K+ channels, adenylyl cyclase, phospholipase Cbeta, phospholipase A2, phosphoinositide 3-kinase and beta-adrenergic receptor kinase
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?
GTP + H2O
GDP + phosphate
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Galpha subunits can regulate intracellular effectors, such as adenylyl cyclase, phospholipase Cbeta, K+ and Ca+ channels, and cyclic GMP phosphodiesterase
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?
GTP + H2O
GDP + phosphate
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Gi1alpha, Gi2alpha and Gi3alpha are capable of preventing stimulation of adenylate cyclase by the alpha2A-adrenoceptor
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?
GTP + H2O
GDP + phosphate
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Gi: the G protein that mediates inhibition of adenylate cyclase
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?
GTP + H2O
GDP + phosphate
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GTPase that functions as a component of the rhodopsin-linked, light-activated phosphodiesterase system
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?
additional information
?
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calcium-independent PKCtheta/delta is a potential downstream target of Galpha12
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?
additional information
?
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analysis of interaction between Capsicum Galpha and Gbeta proteins and between Galpha and RGS activator proteins by yeast split-ubiquitin system
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?
additional information
?
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protein-protein interaction analysis between soybean G-protein subunits, overview. GmGalpha and GmGbeta interact in most of the possible combinations
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?
additional information
?
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Galpha12 and Galpha13 couple with G-protein coupled receptors, GPCRs, for various ligands, e.g. angiotensin II, endothelin, thrombin, bombesin, thromboxane A2, sphingosine-1-phosphate, and lysophosphatidic acid. The coupling specificity between G12 and G13 is usually not strict and most of these ligands can activate both G12 and G13. The RH domain of PDZ-RhoGEF interacts with Galpha13 through multiple intermolecular interfaces. One point of contact is centred on an Ile-Ile-Gly motif found N-terminal to the RGS box. This motif forms multiple contacts with the alpha helical domain of Galpha13, and is conserved in other RH-RhoGEFs. Additionally, Galpha13 interacts with an acidic stretch of residues N-terminal to the core RGS box of PDZ-RhoGEF, overview
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?
additional information
?
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activator/regulator protein R14-RGS by itself shows only a marginal ability to promote GTPase activity
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?
additional information
?
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membrane translocation of RGS8, a regulator of G-protein signaling, depends on interaction of RGS8 with enzyme
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-
?
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NATURAL SUBSTRATE
NATURAL PRODUCT
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate)
(Substrate)
LITERATURE
(Substrate)
(Substrate)
COMMENTARY
(Product)
(Product)
LITERATURE
(Product)
(Product)
REVERSIBILITY
r=reversible
ir=irreversible
?=not specified
r=reversible
ir=irreversible
?=not specified
GTP + H2O
GDP + phosphate
-
Gq/11 is the physiological regulator of phospholipase C-beta1
-
-
?
GTP + H2O
GDP + phosphate
-
intrinsic GTPase activity of transducin controls inactivation of the effector enzyme, cGMP phosphodiesterase during turnoff of the visual signal
-
?
GTP + H2O
GDP + phosphate
-
cycle of G protein activation and deactivation that transmits a signal from receptor to effector: when GDP is bound the alpha subunit associated with the betagamma subunit to form an inactive heterotrimer that binds to the receptor. Both alpha and betagamma subunits can bind to the receptor. When a chemical or physical signal stimulates the receptor, the receptor becomes activated and changes its conformation. The GDP-ligated alpha-subunit responds with a conformational change that decreases GDP affinity, so that GDP is released. Leaving GDP is replaced by GTP. Once ATP is bound, the alpha subunit assumes its activated conformation and dissociates both from the receptor and from betagamma. The activated state lasts until the GTP is hydrolyzed to GDP by the intrinsic GTPase activity of the alpha-subunit. Once GTP is cleaved to GDP, the alpha and betagamma subunits reassociate, become inactive, and return to the receptor. The free alpha and betagamma subunits each activate target effectors. Galphas and Galphaolf, stimulate adenylyl cyclase and regulate Ca2+ channels. Galphai-1, Galphai-2, Galphai-3, Galphao, Galphat-1, Galphat-2, Galphagust and Galphaz inhibit adenylyl cyclase, regulate K+ and Ca2+ channels, and activate cGMP phosphodiesterase. Galphaq, Galpha11, Galpha14, Galppha15 and Galpha16 activate phospholipase C. Galpha12 and Galpha13 regulate Na/K+ exchange. The betagamma subunit is a positive regulator of K+ channels, adenylyl cyclase, phospholipase Cbeta, phospholipase A2, phosphoinositide 3-kinase and beta-adrenergic receptor kinase
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?
GTP + H2O
GDP + phosphate
-
Galpha subunits can regulate intracellular effectors, such as adenylyl cyclase, phospholipase Cbeta, K+ and Ca+ channels, and cyclic GMP phosphodiesterase
-
?
GTP + H2O
GDP + phosphate
-
Gi1alpha, Gi2alpha and Gi3alpha are capable of preventing stimulation of adenylate cyclase by the alpha2A-adrenoceptor
-
?
GTP + H2O
GDP + phosphate
-
Gi: the G protein that mediates inhibition of adenylate cyclase
-
?
GTP + H2O
GDP + phosphate
-
GTPase that functions as a component of the rhodopsin-linked, light-activated phosphodiesterase system
-
-
?
additional information
?
-
-
calcium-independent PKCtheta/delta is a potential downstream target of Galpha12
-
-
?
additional information
?
-
-
protein-protein interaction analysis between soybean G-protein subunits, overview. GmGalpha and GmGbeta interact in most of the possible combinations
-
-
?
additional information
?
-
-
Galpha12 and Galpha13 couple with G-protein coupled receptors, GPCRs, for various ligands, e.g. angiotensin II, endothelin, thrombin, bombesin, thromboxane A2, sphingosine-1-phosphate, and lysophosphatidic acid. The coupling specificity between G12 and G13 is usually not strict and most of these ligands can activate both G12 and G13. The RH domain of PDZ-RhoGEF interacts with Galpha13 through multiple intermolecular interfaces. One point of contact is centred on an Ile-Ile-Gly motif found N-terminal to the RGS box. This motif forms multiple contacts with the alpha helical domain of Galpha13, and is conserved in other RH-RhoGEFs. Additionally, Galpha13 interacts with an acidic stretch of residues N-terminal to the core RGS box of PDZ-RhoGEF, overview
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-
?
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METALS and IONS
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
Al3+
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exposure of the rye roots to Al3+ results in activation of GTPase, Al-induced secretion is inhibited by pertussis toxin
Mg2+
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INHIBITOR
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
Pasteurella multocida toxin
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deamidates glutamine-205 of G alphaI2 to glutamic acid, inhibits intrinsic GTPase activity, causes persistent activation of the G protein
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regulator of G protein signaling protein
Saccharomyces pombe
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Gpa1 signaling suppressed by low stimulation
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betagamma subunit of the hetreotrimeric G protein
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the beta and gamma subunit of G protein form tightly associated complexes, large number of possible combinations of unique beta and gamma subunits, inhibition of steady-state GTP hydrolysis catalyzed by Gsalpha, Goalpha and myristoylated rGialpha2
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betagamma subunit of the hetreotrimeric G protein
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inhibits by selectively binding to and stabilization of the GDP-bound state
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betagamma subunit of the hetreotrimeric G protein
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the beta and gamma subunit of G protein form tightly associated complexes, large number of possible combinations of unique beta and gamma subunits, inhibition of steady-state GTP hydrolysis catalyzed by Gsalpha, Goalpha and myristoylated rGialpha2
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Leu-Gly-Asn repeat-enriched protein
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LGN protein, GDP dissociation inhibitor, GDI, binds to the alpha subunit of transducin in the GDP-bound state
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Leu-Gly-Asn repeat-enriched protein
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LGN protein, GDP dissociation inhibitor, GDI, binds to the alpha subunit of transducin in the GDP-bound state
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pertussis toxin
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a heterotrimeric G-protein antagonist, inhibits the enzyme
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pertussis toxin
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pertussis toxin-catalysed ADP-ribosylation prevents functional contacts between G-protein-coupled receptors and the Gi-like G-proteins
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pertussis toxin
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pertussis toxin-catalysed ADP-ribosylation prevents functional contacts between G-protein-coupled receptors and the Gi-like G-proteins
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pertussis toxin
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a heterotrimeric G-protein antagonist, inhibits the enzyme
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additional information
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GTPase rate is unaffected when transducin alpha-subunit binds to the inhibitory gamma-subunit of cGMP phosphodiesterase, altough this binding is fast and of high affinity
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