| Modification Notes |
Phosphatidylinositol 3-kinase (PI 3-kinase) is composed of p85 and p110 subunits. p85 lacks PI 3-kinase activity and acts as an adapter, coupling p110 to activated protein tyrosine kinase. Two forms of p85 have been described (p85å and p85∫), each possessing one SH3 and two SH2 domains. Various p110 isoforms have been identified. p110å and p110∫ interact with p85å, and p110å has also been shown to interact with p85∫ in vitro. p110∂ expression is restricted to white blood cells. It has been shown to bind p85å and ∫, but it apparently does not phosphorylate these subunits. p110∂ seems to have the capacity to autophosphorylate select amino acid residues, including Tyr 485. p110© does not interact with the p85 subunits. It has been shown to be activated by å and ∫© heterotrimeric G proteins. |