Required to coordinate membrane tubulation with reorganization of the actin cytoskeleton during endocytosis. Homodimerizes, the dimers can polymerize end-to-end to form filamentous structures. Enriched in cortical regions coincident with F-actin. Also localizes to endocytic vesicles and lysosomes. 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.