Fig. 1

Domain organisation of the PI3Ks. Class I, II and III PI3K catalytic subunits share a core region consisting of a C2 domain, helical domain and kinase domain, but differ in other regions of the protein. While the domain structure of the Class IA regulatory subunits is well defined, the Class IB regulatory subunits have no clearly-defined domain structure, while no regulatory subunits have been reported for the Class II PI3Ks. The Class III PI3K, VPS34, associates with a range of accessory proteins to form at least two distinct complexes