Heterotrimeric G protein

From Wikipedia, the free encyclopedia

This heterotrimeric G protein is illustrated with its theoretical lipid anchors. GDP is black. Alpha chain is yellow. Beta and gamma chains are blue.
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
3D structure of a heterotrimeric G protein
An heterotrimeric G protein. GDP is in purple. Alpha chain in orange. Beta chain in blue. Gamma chain in green. An important loop for signal transduction is shown in red (PDB code=1gg2) (more details...)
An heterotrimeric G protein. GDP is in purple. Alpha chain in orange. Beta chain in blue. Gamma chain in green. An important loop for signal transduction is shown in red (PDB code=1gg2) (more details...)

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

Contents

[edit] Alpha subunits

Gα subunits consist of two domains, the GTPase domain, and the alpha-helical domain. There exist at least 20 different Gα subunits, which are separated into four main families. This nomenclature is based on their sequence homologies:[2]

[edit] Beta-gamma complex

The β and γ subunits are closely bound to one another and are referred to as the beta-gamma complex. The Gβγ complex is released from the Gα subunit after its GDP-GTP exchange.

[edit] Function

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

For example, the Gβγ complex, when bound to histamine receptors, can activate phospholipase A2. Gβγ 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.

[edit] Genes

[edit] References

  1. ^ 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. 
  2. ^ 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. PMID 1905812. 

[edit] External links

v • d • e
Acid anhydride hydrolases: GTPases/G proteins (EC 3.6.5)
3.6.5.1: Heterotrimeric G protein
3.6.5.2: Small GTPase > Ras superfamily
3.6.5.3: Elongation factor
3.6.5.5-6: Other
Dynamin (is a GTPase, is not a G protein) - Tubulin
Languages