Crystal packing reveals space for the highly dynamic straight-jacket domain. (a) Overall structure of the biological dimer. Red ovals represent TGFβ-1 and grey rectangles indicate N-terminal elements that are missing in the apo structure. These regions are positioned to approximate the binding position in the latent complex. The bowtie contains two disulfide bonds that connect the biological dimer. RGD (Arg-Gly-Asp) indicates the integrin-binding motif. (b, c) Representative crystal-packing diagrams at orientations of 90° relative to one another. For clarity, one dimer is shown in blue.