Factor XII and kininogen asymmetric assembly with gC1qR/C1QBP/P32 is governed by allostery.

The contact system is composed of factor XII (FXII), prekallikrein (PK), and cofactor high-molecular-weight kininogen (HK). The globular C1q receptor (gC1qR) has been shown to interact with FXII and HK. We reveal the FXII fibronectin type II domain (FnII) binds gC1qR in a Zn2+-dependent fashion and determined the complex crystal structure.