WordNet

any of a large group of nitrogenous organic compounds that are essential constituents of living cells; consist of polymers of amino acids; essential in the diet of animals for growth and for repair of tissues; can be obtained from meat and eggs and milk and legumes; "a diet high in protein"
a unit of force equal to the force exerted by gravity; used to indicate the force to which a body is subjected when it is accelerated (同)gee, g-force
the 7th letter of the Roman alphabet (同)g

PrepTutorEJDIC

蛋白(たんばく)質

Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/12/21 23:58:41」(JST)

wiki en

[Wiki en表示]

This heterotrimeric G protein is illustrated with its theoretical lipid anchors. GDP is black. Alpha chain is yellow. Beta and gamma chains are blue.

3D structure of a heterotrimeric G protein

"G protein" usually refers to the membrane-associated heterotrimeric G proteins, sometimes referred to as the "large" G proteins (as opposed to the subclass of smaller, monomeric small GTPases) . These proteins are activated by G protein-coupled receptors and are made up of alpha (α), beta (β) and gamma (γ) subunits,^[1] the latter two referred to as the beta-gamma complex.

Alpha subunits[edit]

Main article: G alpha subunit

Reconstitution experiments carried out in the early 1980s showed that purified G_α subunits can directly activate effector enzymes. The GTP form of the α subunit of transducin (G_t) activates the cyclic GMP phosphodiesterase from retinal rod outer segments,^[2] and the GTP form of the α subunit of the stimulatory G protein (G_s) activates hormone-sensitive adenylate cyclase.^[3]^[4]

G_α subunits consist of two domains, the GTPase domain, and the alpha-helical domain. There exist at least 20 different G_α subunits, which are separated into four main families. This nomenclature is based on their sequence homologies:^[5]

G-protein-family	α-subunit	Gene	Signal transduction	Use/Receptors (examples)	Effects (examples)
G_i-family
G_i/o	α_i, α_o	GNAO1, GNAI1, GNAI2, GNAI3	Inhibition of adenylate cyclase, opens K⁺-channels (via β/γ subunits), closes Ca²⁺-channels	Muscarinic M₂ and M₄, chemokine receptors, α₂-Adrenoreceptors, Serotonin 5-HT₁ receptors, Histamine H₃ and H₄, Dopamine D₂-like receptors	Smooth muscle contraction, depress neuronal activity
G_t	α_t (Transducin)	GNAT1, GNAT2	Activation of phosphodiesterase 6	Rhodopsin	Vision
G_gust	α_gust (Gustducin)	GNAT3	Activation of phosphodiesterase 6	Taste receptors	Taste
G_z	α_z	GNAZ	Inhibition of adenylate cyclase	?	Maintaining the ionic balance of perilymphatic and endolymphatic cochlear fluids.
G_s-family
G_s	α_s	GNAS	Activation of adenylate cyclase	Beta-adrenoreceptors; Serotonin 5-HT₄, 5-HT₆ and 5-HT₇; Dopamine D₁-like receptors, Histamine H₂	Increase heart rate, Smooth muscle relaxation, stimulate neuronal activity
G_olf	α_olf	GNAL	Activation of adenylate cyclase	olfactory receptors	Smell
G_q-family
G_q	α_q, α₁₁, α₁₄, α₁₅, α₁₆	GNAQ, GNA11, GNA14, GNA15	Activation of phospholipase C	α₁-Adrenoreceptors, Histamine H₁, Serotonin 5-HT₂ receptors, Muscarinic M₁ M₃, and M₅	Smooth muscle contraction, Ca²⁺ flux
G_12/13-family
G_12/13	α₁₂, α₁₃	GNA12, GNA13	Activation of the Rho family of GTPases		Cytoskelatal functions, Smooth muscle contraction

Beta-gamma complex[edit]

Main article: Beta-gamma complex

The β and γ subunits are closely bound to one another and are referred to as the beta-gamma complex. Upon activation of the GPCR, the G_βγ complex is released from the G_α subunit after its GDP-GTP exchange.

Function[edit]

The free G_βγ complex can act as a signaling molecule itself, by activating other second messengers or by gating ion channels directly.

For example, the G_βγ complex, when bound to histamine receptors, can activate phospholipase A₂. G_βγ complexes bound to muscarinic acetylcholine receptors, on the other hand, directly open G protein-coupled inward rectifying potassium channels (GIRKs). They can also activate L-type calcium channels, as in H₃ receptor pharmacology.

References[edit]

^ Hurowitz EH, Melnyk JM, Chen YJ, Kouros-Mehr H, Simon MI, Shizuya H (2000). "Genomic characterization of the human heterotrimeric G protein alpha, beta, and gamma subunit genes". DNA Res 7 (2): 111–20. doi:10.1093/dnares/7.2.111. PMID 10819326.
^ Fung BKK, Hurley, JB, and Stryer, L, 1981. Flow of information in the light-triggered cyclic nucleotide cascade of vision. Proc. Natl. Acad. Sci. USA 78:l52-156 PMID 6264430
^ Cerione RA, Sibley DR, Codina J, Benovic JL, Winslow J, Neer EJ, Birnbaumer L, Caron MG, Lefkowitz RJ, 1984. Reconstitution of a hormone-sensitive adenylate cyclase system. The pure beta-adrenergic receptor and guanine nucleotide regulatory protein confer hormone responsiveness on the resolved catalytic unit. J. Biol. Chem. 259:9979-9982. PMID 6088509.
^ May DC, Ross EM, Gilman AG, Smigel MD, 1985. Reconstitution of catecholamine-stimulated adenylate cyclase activity using three purified proteins. J. Biol. Chem. 260:15829-15833. PMID 2999139.
^ Strathmann MP, Simon MI (1991). "G alpha 12 and G alpha 13 subunits define a fourth class of G protein alpha subunits". Proc. Natl. Acad. Sci. U.S.A. 88 (13): 5582–6. doi:10.1073/pnas.88.13.5582. PMC 51921. PMID 1905812.

External links[edit]

Heterotrimeric G-Proteins at the US National Library of Medicine Medical Subject Headings (MeSH)
EC 3.6.5.1

UpToDate Contents

全文を閲覧するには購読必要です。 To read the full text you will need to subscribe.

1. ペプチドホルモンのシグナル伝達および調節 peptide hormone signal transduction and regulation
2. 高血圧における左室肥大の定義および病因 definition and pathogenesis of left ventricular hypertrophy in hypertension
3. セクレチン secretin
4. 血小板生物学 platelet biology
5. 血管作動性腸管ポリペプチド vasoactive intestinal polypeptide

English Journal

Assessment of Frizzled 6 membrane mobility by FRAP supports G protein coupling and reveals WNT-Frizzled selectivity.

Kilander MB1, Dahlström J1, Schulte G2.
Cellular signalling.Cell Signal.2014 Sep;26(9):1943-9. doi: 10.1016/j.cellsig.2014.05.012. Epub 2014 May 27.
The WNT receptors of the Frizzled family comprise ten mammalian isoforms, bind WNT proteins and mediate downstream signaling to regulate stem cell fate, neuronal differentiation, cell survival and more. WNT-induced signaling pathways are either β-catenin-dependent or -independent, thereby dividing
PMID 24873871

Long-chain base phosphates modulate pollen tube growth via channel-mediated influx of calcium.

Wu J1, Qin X, Tao S, Jiang X, Liang YK, Zhang S.
The Plant journal : for cell and molecular biology.Plant J.2014 Aug;79(3):507-16. doi: 10.1111/tpj.12576. Epub 2014 Jul 9.
Long-chain base phosphates (LCBPs) have been correlated with amounts of crucial biological processes ranging from cell proliferation to apoptosis in animals. However, their functions in plants remain largely unknown. Here, we report that LCBPs, sphingosine-1-phosphate (S1P) and phytosphingosine-1-ph
PMID 24905418

Identification of Receptor Binding-induced Conformational Changes in Non-visual Arrestins.

Zhuo Y1, Vishnivetskiy SA2, Zhan X2, Gurevich VV2, Klug CS3.
The Journal of biological chemistry.J Biol Chem.2014 Jul 25;289(30):20991-1002. doi: 10.1074/jbc.M114.560680. Epub 2014 May 27.
The non-visual arrestins, arrestin-2 and arrestin-3, belong to a small family of multifunctional cytosolic proteins. Non-visual arrestins interact with hundreds of G protein-coupled receptors (GPCRs) and regulate GPCR desensitization by binding active phosphorylated GPCRs and uncoupling them from he
PMID 24867953

Japanese Journal

Transcriptional and Post-transcriptional Mechanisms Limit Heading Date 1 (Hd1) Function to Adapt Rice to High Latitudes

PLOS Genetics 13(1), 2017-01-09
NAID 120005997818

The <i>DENSE AND ERECT PANICLE 1</i> (<i>DEP1</i>) gene offering the potential in the breeding of high-yielding rice

Ｂｒｅｅｄｉｎｇ　Ｓｃｉｅｎｃｅ 66(5), 659-667, 2016
NAID 130005290511

シグナル伝達の選択的な制御を指向したGPCRの構造生命科学

YAKUGAKU ZASSHI 136(2), 179-184, 2016
NAID 130005121475

Related Pictures

★リンクテーブル★

関連記事	「G」「heterotrimeric」「heterotrimer」「Gd」「g」

「G」

Search
PMC	articles
PubMed	articles
NCBI	proteins

Heterotrimeric G-protein GTPase
Identifiers
EC number	3.6.5.1
CAS number	9059-32-9
Databases
IntEnz	IntEnz view
BRENDA	BRENDA entry
ExPASy	NiceZyme view
KEGG	KEGG entry
MetaCyc	metabolic pathway
PRIAM	profile
PDB structures	RCSB PDB PDBe PDBsum
Gene Ontology	AmiGO / EGO
Search
PMC	articles
PubMed	articles
NCBI	proteins