The crystal structures of Mac2 (C; blue), Paip1M (D; red; PDB entry: 3RK6, Lei et al, 2011), and Mac2:Paip1M (E) fit the shape of envelopes derived from the small-angle X-ray scattering (SAXS) data. The blue and red dashed lines indicate the four (GSHM) and seventeen (GSHMASMTGGQQMGRGS) artificial residues remaining from the expression vectors in Mac2 and Paip1M, resp. 