G ( q protein G, or αq G) is a q/11 heterotrimeric G protein subunit that activates phospholipase C (PLC). PLC in turn hydrolyzes Phosphatidylinositol 4,5-bisphosphate (PIP 2) to diacyl glycerol (DAG) and inositol trisphosphate (IP 3) signal transduction pathway. DAG acts as a second messenger that activates Protein Kinase C (PKC) and IP 3 helps in phosphorylation of some proteins. A mnemonic for remembering this subunit is to look at first letter like a backwards "P" (G α = q qhospholipase C).
Function [ edit ]
q proteins are class of G proteins which work to activate phospholipase C (PLC), participating in a variety of cellular signaling pathways. [1 ]
q protein works by activating PLC. PLC then cleaves a phospholipid. In the process, phosphatidylinositol 4,5-bisphosphate (PIP2) is cleaved into diacyl glycerol (DAG) and inositol 1,4,5-trisphosphate (IP 3). DAG remains bound to the membrane, and IP 3 is released as a soluble structure into the cytosol. IP 3 then diffuses through the cytosol to bind to IP, particular 3 receptors calcium channels in the endoplasmic reticulum (ER). These channels are specific to calcium and only allow the passage of calcium to move through. This causes the cytosolic concentration of calcium to increase, causing a cascade of intracellular changes and activity. [1 ]
Further reading: Calcium function in vertebrates
In addition, calcium and DAG together work to activate PKC, which goes on to phosphorylate other molecules, leading to altered cellular activity.
Further reading: function of protein kinase C
Examples of GPCR partners [ edit ]
neurotransmitter receptors ( amine receptors belonging to rhodopsin family), G q has been shown to be pre-coupled with G q-coupled receptors physically and is functionally coupled to e.g. the G-protein coupled receptors: [2 ]
It has been shown that Gq proteins are preassembled (pre-coupled) with Gq-coupled receptors (such as M
3 receptor. The common polybasic domain in the C-tail of Gq-coupled receptors is necessary for the receptor-G protein preassembly. [2 ]
See also [ edit ]
References [ edit ]
External links [ edit ]