Assembly State of Proteasome Activator 28 in an Aqueous Solution as Studied by Small-Angle Neutron Scattering

Abstract

The characterization of quaternary structures of proteins in solution remains challenging, especially for those undergoing dynamic changes. Small-angle neutron scattering (SANS) is a potentially powerful method for addressing this issue with little perturbation resulting from irradiation damage. However, it is usually difficult to determine the three-dimensional (3D) structure of protein complexes at the atomic level on the basis of only SANS data. To cope with this difficulty, we developed a novel approach combining 3D homology modeling with SANS profile simulation, in which whole simulated SANS profiles were examined together with experimental SANS data. We herein demonstrate the feasibilty of our strategy using proteasome activator 28 (PA28) as a model system. PA28 is a hetero-oligomeric protein composed of homologous α- and β-subunits. Although the crystal structure of the homoheptameric ring of α-subunits (PA28α 7 ) has been reported, the physiologically relevant hetero-oligomeric structure remains t...