Crystal structure of IgFLNa21/β2 complex. (A) Electron density map (F_o − F_c) of the β2 peptide calculated from the final model without the peptide, shown at σ = 2. Only β-strands C and D of IgFLNa21 are shown for clarity. (B) The final model of the peptide (orange) built in the electron density map. (C) Overall structure of the IgFLNa21 (gray) and the peptide shown as ribbon diagram. N and C termini are indicated and the β-strands are named. The loop between β-strands D and E that is missing from the final model is indicated with a bracket. (D) Comparison of IgFLNa21/β7 (blue) (PDB entry 2BRQ) and IgFLNa21/β2 (gray and orange) complexes. The numbering of integrin residues is shown.