guanine nucleotide-binding protein (G protein), alpha inhibiting activity polypeptide 1 Identifiers Symbol GNAI1 Entrez 2770 HUGO 4384 OMIM 139310 RefSeq NM_002069 UniProt P63096 Other data Locus Chr. 7 q21-q22

guanine nucleotide-binding protein (G protein), alpha inhibiting activity polypeptide 2 Identifiers Symbol GNAI2 Alt. symbols GNAI2B Entrez 2771 HUGO 4385 OMIM 139360 RefSeq NM_002070 UniProt P04899 Other data Locus Chr. 3 p21

guanine nucleotide-binding protein (G protein), alpha inhibiting activity polypeptide 3 Identifiers Symbol GNAI3 Entrez 2773 HUGO 4387 OMIM 139370 RefSeq NM_006496 UniProt P08754 Other data Locus Chr. 1 p13

G_i alpha subunit (or G_i/G₀ or Gi protein) is a heterotrimeric G protein subunit that inhibits the production of cAMP from ATP.^[1]

Contents 1 Receptors 2 Function 3 Types 3.1 Gia1 3.2 Gia2 3.3 Gia3 4 See also 5 References 6 External links

[edit] Receptors

The following G protein-coupled receptors couple to the G_i subunit:

• Acetylcholine M₂ & M₄ receptors
• Adenosine A₁ & A₃ receptors
• Adrenergic α_2A, α_2B, & α_2C receptors
• Calcium-sensing receptor
• Chemokine CXCR4 receptor
• Dopamine D₂, D₃, D₄
• GABA B₁ & B₂ receptors
• Glutamate mGluR₂, mGluR₃, mGluR₄, mGluR₆, mGluR₇, & mGluR₈ receptors
• Histamine H₃ & H₄ receptors
• Melatonin MT₁, MT₂, & MT₃ receptors
• Opioid δ, κ, μ, & nociceptin receptors
• Prostaglandin EP₁, EP₃, FP, & TP receptors
• Serotonin 5-HT₁ & 5-HT₅ receptors

[edit] Function

See also: function of cAMP-dependent protein kinase

G_i mainly inhibits the cAMP dependent pathway by inhibiting adenylate cyclase activity, decreasing the production of cAMP from ATP, which, in turn, results in decreased activity of cAMP-dependent protein kinase. Thus, the ultimate effect of G_i is, thus, the opposite of cAMP-dependent protein kinase, which can be found at function of cAMP-dependent protein kinase.

It is also attributed a minor role in activation of the phospholipase C pathway, ^[2] Growth hormone is required for normal postnatal growth, bone growth, regulatory effects on protein, carbohydrate, and lipid metabolism.^[3] although this is mainly a function of the G_q alpha subunit.

[edit] Types

There are several types of G_i: Gia1, Gia2, Gia3 and Gia4

[edit] Gia1

Gia1 or G_i1 is encoded by the gene GNAI1.

[edit] Gia2

Gia2 or G_i2 is encoded by the gene GNAI2.

[edit] Gia3

Gia3 or G_i3 is encoded by the gene GNAI3.

[edit] See also

• Second messenger system

[edit] References

[edit] External links

• MeSH Gi+alpha+Subunit

This biochemistry article is a stub. You can help Wikipedia by expanding it. v • d • e

v • d • e Hydrolases: acid anhydride hydrolases (EC 3.6) 3.6.1 Pyrophosphatase (Inorganic, Thiamine) · Apyrase · Thiamine triphosphatase 3.6.2 Adenylylsulfatase · Phosphoadenylylsulfatase 3.6.3-4: ATPase 3.6.3 Cu++ (3.6.3.4) Menkes/ATP7A · Wilson/ATP7B Ca+ (3.6.3.8) SERCA (ATP2A1, ATP2A2, ATP2A3) · Plasma membrane (ATP2B1, ATP2B2, ATP2B3, ATP2B4) · SPCA (ATP2C1, ATP2C2) Na+/K+ (3.6.3.9) ATP1A1 · ATP1A2 · ATP1A3 · ATP1A4 · ATP1B1 · ATP1B2 · ATP1B3 · ATP1B4 H+/K+ (3.6.3.10) ATP4A Other P-type ATPase ATP8B1 · ATP10A · ATP11B · ATP12A · ATP13A2 · ATP13A3 · 3.6.4 Dynein · Kinesin · Myosin 3.6.5: GTPase 3.6.5.1: Heterotrimeric G protein Gαs · Gαi (GNAI1, GNAI2, GNAI3) · Gαq/11 (GNAQ, GNA11) · Gα12/13 (GNA12, GNA13) · Transducin (GNAT1, GNAT2) 3.6.5.2: Small GTPase > Ras superfamily Ras · Rab (Rab27) · Arf (Arf6) · Ran · Rheb · Rho family (RhoA, RhoB, CDC42, Rac1) · Rap 3.6.5.3: Elongation factor Prokaryotic (EF-Tu, EF-Ts, EF-G) · Eukaryotic 3.6.5.5-6: Other Dynamin (is a GTPase, is not a G protein) · Tubulin