A comparison between the crystal and solution structures of Escherichia coli asparaginase II

The small angle X-ray scattering (SAXS) pattern of the homotetrameric aspa­raginase II from Escherichia coli was measured in solution in conditions resembling those in which its crystal form was obtained and compared with that calculated from the crystallographic model. The radius of gyration measured by SAXS is about 5% larger and the maximum dimension in the distance distribution function about 12% larger than the corresponding value calculated from the crystal structure. A compari­son of the experimental and calculated distance distribution functions suggests that the overall quaternary structure in the crystal and in solution are similar but that the homotetramer is less compact in solution than in the crystal.