| Type: | Domain | Name: | G protein alpha subunit, helical insertion |
| Description: | Guanine nucleotide binding proteins (G proteins) are membrane-associated, heterotrimeric proteins composed of three subunits: alpha (), beta () and gamma () []. G proteins act as signal transducers, relaying a signal from a ligand-activated GPCR (G protein-coupled receptor) to an enzyme or ion channel effector. The activated GPCR promotes the exchange of GDP for GTP on the G protein alpha subunit, allowing the trimeric G protein to be released from the receptor and to dissociate into active (GTP-bound) alpha subunit and beta/gamma dimer, both of which activate distinct downstream effectors. There are several isoforms of each subunit, which together can makeup hundreds of combinations of G proteins, each one linking a specific receptor to a certain effector.The heterotrimeric G protein alpha subunit is composed 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 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 []. This entry represents the G protein alpha subunit helical insertion domain. | Short Name: | GproteinA_insert |
| DB identifier | Type | Name |
|---|---|---|
| IPR001019 | Family | Guanine nucleotide binding protein (G-protein), alpha subunit |
| 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 |
