Editing G protein (section)

== Function ==
G proteins are important [[signal transducing]] molecules in cells. "Malfunction of GPCR [G Protein-Coupled Receptor] signaling pathways are involved in many diseases, such as [[diabetes]], blindness, allergies, depression, cardiovascular defects, and certain forms of [[cancer]]. It is estimated that about 30% of the modern drugs' cellular targets are GPCRs."<ref name="Bosch_2013">{{cite journal | vauthors = Bosch DE, Siderovski DP | title = G protein signaling in the parasite Entamoeba histolytica | journal = Experimental & Molecular Medicine | volume = 45 | issue = 1038 | pages = e15 | date = March 2013 | pmid = 23519208 | doi = 10.1038/emm.2013.30 | pmc=3641396}}</ref> The human genome encodes roughly 800<ref name="Baltoumas_2013">{{cite journal | vauthors = Baltoumas FA, Theodoropoulou MC, Hamodrakas SJ | title = Interactions of the α-subunits of heterotrimeric G-proteins with GPCRs, effectors and RGS proteins: a critical review and analysis of interacting surfaces, conformational shifts, structural diversity and electrostatic potentials | journal = Journal of Structural Biology | volume = 182 | issue = 3 | pages = 209–18 | date = June 2013 | pmid = 23523730 | doi = 10.1016/j.jsb.2013.03.004 }}</ref> [[G protein-coupled receptors]], which detect photons of light, hormones, growth factors, drugs, and other endogenous [[Ligand (biochemistry)|ligands]].  Approximately 150 of the GPCRs found in the human genome still have unknown functions.

Whereas G proteins are activated by [[G protein-coupled receptor]]s, they are inactivated by [[Regulator of G protein signalling|RGS proteins]] (for "Regulator of G protein signalling"). Receptors stimulate GTP binding (turning the G protein on). RGS proteins stimulate GTP hydrolysis (creating GDP, thus turning the G protein off).