Gi alpha subunit

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G protein subunit alpha i1
Symbol GNAI1
Entrez 2770
HUGO 4384
OMIM 139310
RefSeq NM_002069
UniProt P63096
Other data
Locus Chr. 7 q21-q22
G protein subunit alpha i2
Symbol GNAI2
Entrez 2771
HUGO 4385
OMIM 139360
RefSeq NM_002070
UniProt P04899
Other data
Locus Chr. 3 p21
G protein subunit alpha i3
Symbol GNAI3
Entrez 2773
HUGO 4387
OMIM 139370
RefSeq NM_006496
UniProt P08754
Other data
Locus Chr. 1 p13
G protein subunit alpha o1
Symbol GNAO1
Entrez 2775
HUGO 4389
OMIM 139311
RefSeq NM_020988
UniProt P09471
Other data
Locus Chr. 16 q13

Gi alpha subunit (Gαi, or Gi/G0 or Gi protein) is a heterotrimeric G protein subunit that inhibits the production of cAMP from ATP.[1] A mnemonic for remembering this subunit is to look at first letter (Gαi = Adenylyl Cyclase inhibitor).


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


Gi 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. Therefore, the ultimate effect of Gi is the opposite 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 Gq alpha subunit.


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


Gia1 or Gi1 is encoded by the gene GNAI1.


Gia2 or Gi2 is encoded by the gene GNAI2.


Gia3 or Gi3 is encoded by the gene GNAI3.

See also[edit]


  1. ^ Birnbaumer L (April 2007). "Expansion of signal transduction by G proteins. The second 15 years or so: from 3 to 16 alpha subunits plus betagamma dimers". Biochim. Biophys. Acta. 1768 (4): 772–93. PMC 1993906Freely accessible. PMID 17258171. doi:10.1016/j.bbamem.2006.12.002. 
  2. ^ Obál F, Krueger J (2001). "The somatotropic axis and sleep.". Rev Neurol (Paris). 157 (11 Pt 2): S12–5. PMID 11924022. 
  3. ^ GeneGlobe -> GHRH Signaling[permanent dead link] Retrieved on May 31, 2009

External links[edit]