Figure 2: Dimerization interface of xZNRF3ecto.

(a) View along the twofold axis away from the putative membrane. (b) xZNRF3ecto–xRspoFu1–Fu2 complex with close-up view onto the β1–β2 hairpin arm (‘clamp’) embracing the respective other protomer. This interface is stabilized by binding of Rspo to ZNRF3 and subsequent structuring of the acidic region of the β3–β4 loop drawn in red. Residue numbers refer to mouse proteins.