 In the Golgi apparatus, PtdIns4"P" binds to the GTP-binding protein ARF and to effector proteins, including four-phosphate-adaptor protein 1 and 2 (FAPP1 and FAPP2).This three molecule complex recruits proteins that need to be carried to the cell membrane.There is now evidence that PI-4-P is capable of deforming lipid systems into tightly curved assemblies, this is consistent with similar behaviour observed in phosphatidylinositol.