P27986, Q92569

Phosphatidylinositol 3-kinase (PI 3-kinase) phosphorylates the 3′ OH position of the inositol ring of inositol lipids and is composed of p85 and p110 subunits. PI 3-kinase p85 lacks PI 3-kinase activity and acts as an adapter, coupling p110 to activated protein tyrosine kinase. Both PI 3-kinase p85α and PI 3-kinase p85β possess one SH3 and two SH2 domains. PI 3-kinase p85α, also known as GRB1, phosphatidylinositol 3-kinase regulatory 1 or p85, is a 724 amino acid protein that exists as four alternatively spliced isoforms. Involved in insulin metabolism, defects in the PI 3-kinase p85α gene have been linked to insulin resistance. PI 3-kinase p85α is polyubiquitinated in T cells by Cbl-b, and has multiple phosphorylated amino acid residues, including a phosphorylated tyrosine residue at position 467. PI 3-kinase p85γ contains 1,102 amino acids and is encoded by a gene that maps to human chromosome 7.