Cooperative Membrane Recognition by Lipid-Sensing and Kinase Domains Shapes Membrane-Bound States of AKT

Although AKT is a multidomain serine/threonine kinase composed of an N-terminal pleckstrin homology (PH) domain and a C-terminal kinase domain (KD), how these domains cooperate to regulate AKT activation on membranes remains unclear at the molecular level. Here, using molecular dynamics simulations of full-length AKT on phosphatidylinositol (3,4,5)-trisphosphate (PIP₃)-containing lipid bilayers, we identify four distinct membrane-binding modes that differ in the orientations and membrane contacts of the PH domain and KD.

In addition to PIP₃ binding to the PH domain, we observed specific PIP₃ interactions with basic residues in the KD. In the most stable mode, PIP₃ interacts with both the canonical and a secondary binding site in the PH domain, while the KD adopts an orientation in which the activation loop phosphorylation site is exposed to the solvent. The populations of these binding modes depend on the PIP₃ concentration in the membrane, leading to changes in the preferred orientation of AKT.