Model of VWF tubules. (A) The tubule structure of D1D2 with the small holes formed by a donut-shaped D1D2 dimer (cyan) for the docking of D’D3 dimers (left). D’D3 dimers (purple) decorate the out surface of the D1D2 tubule (middle). The conventional repeating unit with 1 D’D3 dimer and 1 D1D2 dimer is highlighted in the full VWF tubule (right). Scale bar, 22 and 28 nm. (B) An alternative view of the tubules formed by D1D2. The pH-sensitive D1D2 dimer is colored cyan (left). D’D3 dimers similarly docked in the smaller holes of the tubule (middle). A pH-sensitive D1D2 homodimer loaded with 2 D’D3 monomers in the full VWF tubule is highlighted with D1D2 in cyan and D’D3 in purple. (C) The distance between the 2 ends of D3 domains is ∼20 nm. The 2 C-terminal tails of mature VWF covalently linked by the CK domains will form a spike-like structure (dashed lines) pointing toward the outside of tubule, which makes the full VWF tubule look like a round brush. Scale bar, 20 nm.