Required to coordinate membrane tubulation with reorganization of the actin cytoskeleton during endocytosis. May bind to lipids such as phosphatidylinositol 4,5-bisphosphate and phosphatidylserine and promote membrane invagination and the formation of tubules. Also promotes CDC42-induced actin polymerization by activating the WASL-WASPIP complex, the predominant form of WASL/N-WASP in cells. Actin polymerization may promote the fission of membrane tubules to form endocytic vesicles. Essential for autophagy of intracellular bacterial pathogens (By similarity). Homodimerizes, the dimers can polymerize end-to-end to form filamentous structures. Interacts with GTP-bound CDC42. Interacts with DAAM1, DIAPH1, DIAPH2, DNM1, DNM2 and WASL/N-WASP. Interacts with ATG3. Interacts (via SH3 domain) with ABI1, WASF2, CDC42 and WIPF1. The F-BAR domain binds the phospholipid membrane with its concave surface. The end-to-end polymerization of dimers of these domains provides a curved surface that fits best membranes with around 600 A diameter, and may drive tubulation (By similarity). Belongs to the FNBP1 family.