X-ray scattering studies of metalloproteins in solution: a quantitative approach for studying molecular conformations

The model-independent approach based on the multipole expansion method using spherical harmonics [Stuhrmann (1970a). Acta Cryst. A26, 297-306] has been applied to obtain structural information on a variety of metalloproteins studied by synchrotron X-ray solution scattering. The method is applied to examples (nitrite reductase, transferrin and nitrogenase), not only with the view of comparing protein conformations in solution with those in the crystalline state, but also defining conformational changes and protein-protein interactions which are of functional importance. The shape restoration is found to be straightforward at low resolution (L less than or equal to 3). For correct treatment using higher harmonics, overall molecular symmetry, if present, must be included in the multipole expansion.