Phosphatidylinositol 4-kinase IIα (PI4K IIα) is one of the four mammalian lipid kinases that catalyses the conversion of phosphatidylinositol to phosphatidylinositol 4 phosphate, the major precursor of phosphoinositides. PI4K IIα is a constitutively active membrane bound protein and its catalytic activity is responsive to the membrane composition. It was shown that PI4K IIα has an important role in intracellular vesicular trafficking, inter-organelle trafficking and signal transduction. Furthermore, PI4K IIα is indispensable for neuronal survival and regulation of tumor growth. Due to an emerging role of PI4K IIα in several diseases and in maintaining the phosphoinositide homeostasis in the cell there has been a strong interest in its structural determination. In addition, there are currently no isoform-specific inhibitors of PI4K available to modulate their overlapping enzymatic activity and thereby enable the proper isoform-specific characterisation in different cell compartments. Therefore, here we present the structural domain composition of PI4K IIα with ATP in the active site. The crystal structure revealed conserved N- and C-terminal lobes with ATP binding site located at their interface and the unique hydrophobic pocket of the C-lobe with second bound ATP. We further used the MD simulation and site-directed mutagenesis to analyze structural features determining substrate specificity and membrane binding mode.
This study was supported by the MarieCurie FP7-PEOPLE-2012-CIG (project number: 333916).