The ephrin-B2 W122 “latch”.

Two rotameric W122 (ephrin-B2) conformations in the HeV-G/ephrin-B2 complex, both of which are distinct from the W122 conformation in unbound ephrin-B2. Ephrin-B2 is shown in silver in the unbound state, and in yellow or cyan in the two complexes with HeV-G (A). W122 transforms from the initial unbound conformation to an intermediate conformation upon binding to HeV-G due to steric and electrostatic constrains, then adopts its final conformation via stabilizing van der Waals interactions with HeV-G. W122 is shown as yellow sticks. G is shown as a surface colored according to its electrostatic potential (B). “Latch up” and “latch down” conformations of ephrin-B2-W122 mediate the association and dissociation of the HeV-G/ephrin-B2 complex. Ephrin-B2-W122 is shown in yellow, HeV-G - in grey (C).