Figure 1.

Structure of the F-spondin domain of mindin and comparison with a Ca²⁺-dependent C2 domain. (A) Side view of mindin-FS (ribbon diagram). The two four-stranded β-sheets, β6β5β2β3 (front) and β4β1β8β7 (back), are green and blue, respectively. Helices α1 and α2 are red. The bound Ca²⁺ ion is yellow. Loops L1–L4 at the top of the molecule are cyan. Residues mutated to alanine to localize the integrin-binding site are drawn in ball-and-stick representation, with carbon atoms in yellow, oxygen atoms in red and nitrogen atoms in blue. (B) Mindin-FS is rotated ∼180° about the vertical axis with respect to the view in (A). (C) Side view of the C2 domain of cytosolic phospholipase A₂ (PDB accession code 1RLW). The orientation is similar to that of mindin-FS in (B). The two four-stranded β-sheets, β4β1β8β7 (front) and β6β5β2β3 (back), are blue and green, respectively. The bound Ca²⁺ ion is yellow. Calcium-binding loops CBR1–CBR3 are cyan.