FIGURE 1.

LFA-1 conformations. Integrin function is structurally regulated and three distinct conformations have been demonstrated. In its low affinity state (left), LFA-1 is compact with a sharp bend at the “genu” and headpiece closely approaching the plasma membrane. Extended conformations (middle) differ in the orientation of their hybrid domain (purple), with swingout of this domain representing a conversion from intermediate to high affinity state (right). Data suggest that the extended/closed conformation (middle) can have either a low or intermediate affinity αI domain.