Diverse dimerization mechanisms among VWF CTCK and its relatives. Dimer structures are superimposed on the CTCK monomer in cyan and then aligned with it horizontally and vertically on the page. Disulfide bonds are shown in stick and colored as in Figure 1. (A) VWF CTCK. (B) Human chorionic gonadotropin (PDB code 1QFW). (C) Neurotrophin-4 (PDB 1HCF). (D) Noggin (PDB 1M4U). (E) TGFβ2 (PDB 1TFG). (F) PDGF (PDB 1PDG).