Protein Domain : IPR001019

Type:  Family Name:  Guanine nucleotide binding protein (G-protein), alpha subunit
Description:  Guanine nucleotide binding proteins (G proteins) are membrane-associated, heterotrimeric proteins composed of three subunits: alpha (), beta () and gamma () []. G proteins and their receptors (GPCRs) form one of the most prevalent signalling systems in mammalian cells, regulating systems as diverse as sensory perception, cell growth and hormonal regulation []. At the cell surface, the binding of ligands such as hormones and neurotransmitters to a GPCR activates the receptor by causing a conformational change, which in turn activates the bound G protein on the intracellular-side of the membrane. The activated receptor promotes the exchange of bound GDP for GTP on the G protein alpha subunit. GTP binding changes the conformation of switch regions within the alpha subunit, which allows the bound trimeric G protein (inactive) to be released from the receptor, and to dissociate into active alpha subunit (GTP-bound) and beta/gamma dimer. The alpha subunit and the beta/gamma dimer go on to activate distinct downstream effectors, such as adenylyl cyclase, phosphodiesterases, phospholipase C, and ion channels. These effectors in turn regulate the intracellular concentrations of secondary messengers, such as cAMP, diacylglycerol, sodium or calcium cations, which ultimately lead to a physiological response, usually via the downstream regulation of gene transcription. The cycle is completed by the hydrolysis of alpha subunit-bound GTP to GDP, resulting in the re-association of the alpha and beta/gamma subunits and their binding to the receptor, which terminates the signal []. The length of the G protein signal is controlled by the duration of the GTP-bound alpha subunit, which can be regulated by RGS (regulator of G protein signalling) proteins () or by covalent modifications [].G protein alpha subunits are 350-400 amino acids in length and have molecular weights in the range 40-45 kDa. Seventeen distinct types ofalpha subunit have been identified in mammals. These fall into 4 main groups on the basis of both sequence similarity and function: alpha-S (), alpha-Q (), alpha-I ()and alpha-12() [].The specific combination of subunits in heterotrimeric G proteins affects not only which receptor it can bind to, but also which downstream target is affected, providing the means to target specific physiological processes in response to specific external stimuli [, ]. G proteins carry lipid modifications on one or more of their subunits to target them to the plasma membrane and to contribute to protein interactions.This family consists of the G protein alpha subunit, which acts as a weak GTPase. G protein classes are defined based on the sequence and function of their alpha subunits, which in mammals fall into four main categories: G alpha-S (), G alpha-Q (), G alpha-I () and G alpha-12 (); there are also fungal () and plant classes () of alpha subunits.Many alpha subunits are substrates for ADP-ribosylation by cholera or pertussis toxins. They are often N-terminally acylated, usually with myristate and/or palmitoylate, and these fatty acid modifications are probably important for membrane association and high-affinity interactions with other proteins. The alpha subunit consists of two domains: a GTP-binding domain and a helical insertion domain (). The GTP-binding domain is homologous to Ras-like small GTPases, and includes switch regions I and II, which change conformation during activation. The switch regions are loops of alpha-helices with conformations sensitive to guanine nucleotides. The helical insertion domain is inserted into the GTP-binding domain before switch region I and is unique to heterotrimeric G proteins. This helical insertion domain functions to sequester the guanine nucleotide at the interface with the GTP-binding domain and must be displaced to enable nucleotide dissociation. Short Name:  Gprotein_alpha_su
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6 Child Features

DB identifier Type Name
IPR002976 Family Plant G-protein, alpha subunit
IPR002975 Family Fungal G-protein, alpha subunit
IPR000367 Family G-protein alpha subunit, group S
IPR000469 Family G-protein alpha subunit, group 12
IPR000654 Family G-protein alpha subunit, group Q
IPR001408 Family G-protein alpha subunit, group I

1 Contains

DB identifier Type Name
IPR011025 Domain G protein alpha subunit, helical insertion

4 Cross Referencess

Identifier
PTHR10218
PF00503
PR00318
SM00275

0 Found In

5 GO Annotations

GO Term Gene Name
GO:0003924 IPR001019
GO:0004871 IPR001019
GO:0019001 IPR001019
GO:0031683 IPR001019
GO:0007186 IPR001019

5 Ontology Annotations

GO Term Gene Name
GO:0003924 IPR001019
GO:0004871 IPR001019
GO:0019001 IPR001019
GO:0031683 IPR001019
GO:0007186 IPR001019

0 Parent Features

3256 Proteins

DB identifier UniProt Accession Secondary Identifier Organism Name Length
82143 PAC:15408878 Selaginella moellendorffii 835  
169732 PAC:15404997 Selaginella moellendorffii 723  
75723 PAC:15415079 Selaginella moellendorffii 354  
evm.TU.contig_39682.1 PAC:16431370 Carica papaya 108  
evm.model.supercontig_126.8 PAC:16407361 Carica papaya 261  
evm.model.supercontig_126.5 PAC:16407354 Carica papaya 122  
evm.model.supercontig_16.6 PAC:16410095 Carica papaya 308  
evm.model.supercontig_16.9 PAC:16410128 Carica papaya 518  
evm.model.supercontig_3.351 PAC:16416648 Carica papaya 873  
evm.model.supercontig_62.86 PAC:16424052 Carica papaya 920  
29739.m003634 B9RQY3 PAC:16807414 Ricinus communis 392  
29851.m002477 B9RZF5 PAC:16811503 Ricinus communis 928  
30068.m002662 B9RZ26 PAC:16816669 Ricinus communis 1203  
29676.m001681 B9S8Q3 PAC:16805426 Ricinus communis 917  
28613.m000141 B9T5D0 PAC:16801253 Ricinus communis 846  
Cucsa.322150.2 A0A0A0L523 PAC:16977695 Cucumis sativus 864  
Cucsa.322150.1 A0A0A0L523 PAC:16977694 Cucumis sativus 864  
Cucsa.109960.1 PAC:16959965 Cucumis sativus 876  
Cucsa.112140.1 PAC:16960143 Cucumis sativus 878  
Cucsa.102030.1 PAC:16958789 Cucumis sativus 967  
Cucsa.102030.2 A0A0A0KJD5 PAC:16958790 Cucumis sativus 966  
Cucsa.102030.3 A0A0A0KJD5 PAC:16958791 Cucumis sativus 966  
Cucsa.271110.1 A0A0A0L2X2 PAC:16973482 Cucumis sativus 392  
Cucsa.271110.2 A0A0A0L2X2 PAC:16973483 Cucumis sativus 392  
Cucsa.271110.3 PAC:16973484 Cucumis sativus 317  
orange1.1g002836m PAC:18091037 Citrus sinensis 875  
orange1.1g003444m A0A067GIC0 PAC:18124890 Citrus sinensis 819  
orange1.1g004481m A0A067GL39 PAC:18124891 Citrus sinensis 750  
orange1.1g016288m A0A067G234 PAC:18125928 Citrus sinensis 392  
orange1.1g018283m A0A067GE74 PAC:18125930 Citrus sinensis 358  

7 Publications

First Author Title Year Journal Volume Pages PubMed ID
            1902986
            15294442
            15119945
            14762218
            11313912
            9278091
            11882385