F-BAR, N-BAR and I-BAR family domain structure and membrane curvature models. BAR domain superfamily consists of three families based on distinct domain structures of F-BAR, N-BAR, and I-BAR. Bar domain proteins can form homodimer which binds to cell membrane leading to membrane curvature. (A) Domain structures of F-BAR family. F-BAR family has nine subfamilies determined by the specific domain combination. (B) Domain structures of N-BAR family. (C) Domain structures of I-BAR family. (D) Membrane curvature forms caused by BAR domain proteins. F-BAR, N-BAR, and I-BAR proteins bind to cell membrane and lead to different forms of curvature changes. Domain information is based on previous publications [1,3,4,7,8]. Crystal structure (a red monomer and a green monomer forming a dimer) is generated by using Protein Data Bank (PDB, http://www.rcsb.org/pdb/home/home.do). Abbreviations: BAR, Bin/Amphiphysin/Rvs; CRIB, CDC42-Rac interactive binding; F-BAR, Fes/CIP4 homology-BAR; FX, F-BAR extension; HR1, Protein kinase C-related kinase homology region 1; I-BAR, Inverse BAR; N-BAR, N-terminal amphipathic helix BAR; NPF, Asparagine proline phenylalanine; RhoGAP, Rho GTPase-activating protein; SH2, Src homology-2; SH3, Src homology-3; WH2, WASP homology 2; Tyr-kinase, Tyrosine kinase; μHD, μ-homology domain. Symbols listed in the framed box indicate representative domains.