Gi alpha subunit

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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

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Overview

G_i alpha subunit (or G_i/G₀ or Gi protein) is a heterotrimeric G protein subunit which inhibits the production of cAMP from ATP.

Receptors

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

• 5-HT receptor type 1
• Adenosine receptor A1 and A3
• Prostaglandins

Function

Further reading: function of cAMP-dependent protein kinase

G_i inhibits 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.

Types

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

Gia1

Gia1 or G_i1 is encoded by the gene GNAI1.

Gia2

Gia2 or G_i2 is encoded by the gene GNAI2.

Gia3

Gia3 or G_i3 is encoded by the gene GNAI3.

See also

• Second messenger system

External links

• MeSH Gi+alpha+Subunit

v • d • e Acid anhydride hydrolases: GTPases/G proteins (EC 3.6.5)
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 - Eukaryotic
3.6.5.5-6: Other	Dynamin (is a GTPase, is not a G protein) - Tubulin