High-resolution crystal structures of the headpiece of lymphocyte function-associated antigen-1 (integrin ?L?2) reveal how the ?I domain interacts with its platform formed by the ?-subunit ?-propeller and ?-subunit ?I domains. The ?L?2 structures compared with ?X?2 structures show that the ?I domain, tethered through its N-linker and a disulfide to a stable ?-ribbon pillar near the center of the platform, can undergo remarkable pivoting and tilting motions that appear buffered by N-glycan decorations that differ between ?L and ?X subunits. Rerefined ?2 integrin structures reveal details including pyroglutamic acid at the ?2 N terminus and bending within the EGF1 domain. Allostery is relayed to the ?I domain by an internal ligand that binds to a pocket at the interface between the ?-propeller and ?I domains. Marked differences between the ?L and ?X subunit ?-propeller domains concentrate near the binding pocket and ?I domain interfaces. Remarkably, movement in allostery in the ?I domain of specificity determining loop 1 (SDL1) causes concerted movement of SDL2 and thereby tightens the binding pocket for the internal ligand.