This entry represents the N-terminal domain of PI3-kinase catalytic subunit gamma (PIK3CG, also known as p110 catalytic subunit gamma). This domain contains the adaptor-binding domain (ABD). PIK3CG interacts with the regulatory subunit of the p101 type [, , ].Phosphatidylinositol 3-kinases (PI3Ks) are lipid kinases that phosphorylate 4,5-bisphonate (PI(4,5) P2 or PIP2) at the 3-position of the inositol ring, and thus generate phosphatidylinositol 3,4,5-trisphosphate (PIP3), which, in turns, initiates a vast array of signaling events. PI3Ks can be grouped into three classes based on their domain organisation. Class I PI3Ks are heterodimers consisting of a p110 catalytic subunit and a regulatory subunit of either the p85 type (associated with the class IA p110 isoforms p110alpha, p110beta or p110delta) or the p101 type (associated with the class IB p110isoform p110gamma). Common to all catalytic subunits are an N-terminal adaptor-binding domain (ABD) that binds to p85/p101, a Ras-binding domain (RBD), a putative membrane-binding domain (C2), a helical domain of unknown function, and a kinase catalytic domain [, , ].PI3K_ABD is a small globular domain of about 100 residues in length with an alpha/β-sandwich topology [, , ].