Binds to membranes enriched in phosphatidylinositol 3-phosphate (PtdIns(P3)) and phosphatidylinositol 4,5-bisphosphate. May be involved in several stages of intracellular trafficking. Monomer. Highly expressed in fetus liver, but only weakly expressed in brain, skeleton muscle, smooth muscle, and cardiac muscle, kidney, and adrenal gland. The PX domain mediates specific binding to membranes enriched in phosphatidylinositol 3-phosphate (PtdIns(P3)). Belongs to the sorting nexin family.