Fig. 1.

LFA-1 headpiece structure. (A) Representative LFA-1 headpiece structure [crystal in Mg formate, Protein Data Bank (PDB) ID code 5E6U]. Ribbon cartoon with disulfides as gold sticks, glycans as white sticks with red oxygens, and Ca²⁺ and Mg²⁺ as gold and silver spheres, respectively. βI domain metal binding sites of (B) LFA-1 crystal in Mg formate and (C) internally liganded α_Xβ₂ crystal (PDB ID code 4NEH). (D) β-subunit domain orientation differences shown after superposition on the βI domain of the two most dissimilar LFA-1 headpiece examples (cyan, PDB ID codes 5E6S and 5E6U), rerefined closed–bent α_Xβ₂ ectodomain (orange, PDB ID code 5ES4), and internally liganded bent α_Xβ₂ ectodomain (red). (E) Interface between the PSI (green) and I-EGF1 (wheat) domains in PDB ID code 5E6U. (F) N-terminal pyroglutamic acid (PDB ID code 5E6V). Mesh shows 1σ 2Fo–Fc density.