IDENTIFICATION OF A PHOSPHATIDYLINOSITOL-4,5-BISPHOSPHATE-BINDING DOMAIN IN THE N-TERMINAL REGION OF EZRIN

Purified human recombinant ezrin cosediments with large liposomes cont aining phosphatidylserine (PS). This interaction is optimal at low ion ic strength. At physiological ionic strength (130 mM KCI) ezrin intera cts strongly with liposomes containing greater than or equal to 5% pho sphatidylinositol-4,5-bisphosphate (PIP2), the residual being phosphat idylcholine (PC). When PIP2 is replaced by phosphatidylinositol-4-mono phosphate (PIP), phosphatidylinositol (PI) or PS, the interaction is m arkedly reduced. Furthermore we show, that a purified N-terminal gluta thione S-transferase (GST) fusion protein of ezrin (1-309) still has r etained the capacity to interact with PIP2-containing liposomes, where as a C-terminal fusion protein (310-586) has lost this ability.