Identification of a phosphatidylinositol-4,5-bisphosphate-binding domain in the N-terminal region of ezrin

Purified human recombinant ezrin cosediments with large liposomes containing phosphatidylserine (PS). This interaction is optimal at low ionic strength. At physiological ionic strength (130 mM KCl) ezrin interacts strongly with liposomes containing > or = 5% phosphatidylinositol-4,5-bisphosphate (PIP2), the residual being phosphatidylcholine (PC). When PIP2 is replaced by phosphatidylinositol-4-monophosphate (PIP), phosphatidylinositol (PI) or PS, the interaction is markedly reduced. Furthermore we show, that a purified N-terminal glutathione S-transferase (GST) fusion protein of ezrin (1-309) still has retained the capacity to interact with PIP2-containing liposomes, whereas a C-terminal fusion protein (310-586) has lost this ability.