Organization of VWF within a tubule. (A) Cryo-EM map of the dimer-derived VWF tubule in gray with a single bead colored by each of the 4 monomeric VWF subunits from which it is formed. Beads have twofold symmetry. (B) A single bead. The left view has the same orientation as in (A) and has a red dashed line separating symmetrical halves. The right view shows the luminal facing portion of the bead, which is formed by 2 antiparallel D1D2 prodomains that form a cradle for the binding of 2 juxtaposed D′D3 domains. (C) A VWF monomer, colored by domain, adopts an extended conformation that spans 2 beads. The D1D2 prodomain is in 1 bead, and the D′D3 and A1 domains are in a neighboring bead. Domains of neighboring VWF molecules are colored gray and are shown with thinner loops, helices, and strands.