Fig. 6. Multiple states of the bound E2~Ub conjugate.

The structures of Ark2C in complex with UbcH5b~Ub conjugate in an open (PDB: 5D0K), closed but not primed (PDB: 5D0M) and closed and primed conformation was overlayed. The primed complex structure is shown together with Ub^D for all three structures as indicated. Ub^R from the open and primed structures is also included to show the displacement that occurs upon binding. Below the contacts between Ub^D and the crossover helix of the E2, as well as the linchpin arginine, are highlighted. The buried surface area for Ub^D in the three structures is 170, 640 and 970 Ų for the Open, Intermediate and Activated states.