Inner membrane clasp and outer membrane clasp of LFA-1. (A) The inhibitory salt bridge of IMC (electrostatic interaction between the αL-R1094 and β2-D709) and the outer membrane clasp (helical packing) mediated by glycine in the TMDs. (B) Simulated αLβ2 dimer structures. The side chains of major residues involved in dimerization are shown in sticks. (C) Trimeric interaction among αL, β2, and POPS (1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-l-serine). The lipid phosphate group simultaneously engages the β2-K702 amino group and the αL-R1094 guanidino group. Panels B and C are adapted from Guo et al.⁸¹