Site-Specific Phosphorylation of RTK KIT Kinase Insert Domain: Interactome Landscape Perspectives

The kinase insert domain (KID) of RTK KIT is a key recruitment region for downstream signalling proteins (DSPs). KID, as a multisite phosphorylation region, provides alternative recognition sites for DSPs and activates them by binding a phosphotyrosine (pY) to their SH2 domains. Significant steric, biochemical, and biophysical requirements must be fulfilled by each pair of interacting proteins as the adaptation of their configurations is mandatory for the selective activation of DSPs. The accurate 3D atomistic models obtained by modelling and molecular dynamics (MD) simulations of phosphorylated KID (p-KID) have been delivered to describe KID INTERACTOME. By taking phosphorylated KIDpY721 and the N-terminal SH2 domain of phosphatidylinositol 3-kinase (PI3K), a physiological partner of KID, we showed the two proteins are intrinsically disordered. Using 3D models of both proteins, we probe alternative orientations of KIDpY721 relative to the SH2 binding pocket using automatic docking (HADDOCK) and intuitive user-guided docking. This modelling yields to two possible models of the functionally related non-covalent complex KIDpY721/SH2, where one can be regarded as the first precursor to probe PI3K activation via KIT KID. We suggest that such generation of a KID/SH2 complex is best suited for future studies of the post-transduction effects of RTK KIT.