Structure of type II-beta phosphatidylinositol phosphate kinase: a protein kinase fold flattened for interfacial phosphorylation

The structure of type II-beta phosphatidylinositol phosphate kinase (PIPK) shows a protein kinase ATP-binding core. It indicates that all phosphoinositide kinases are part of one superfamily. The flatness of the membrane-binding site, along with the shallowness of the substrate-binding pocket and its closeness to the membrane indicate that PIPKs phosphyorylate their substrates in situ in membranes. This allows the enzyme to avoid an energetic penalty for removing the substrate from its low-energy conformation within the membrane.