Its function is regulated by several Proteasome Activators (PAs). For example, PA28 binds to proteasomes and the resulting complex promotes the production of immune-response peptides. PA28 is known to comprise seven-membered rings containing two very similar subunits, named a and b, each of molecular weight ~28 kDa. Novel insight into the structure of PA28 has been obtained in small-angle neutron scattering (SANS) experiments carried out on the recently commissioned Second Target Station instrument Sans2d. Employing water-solvent contrast variation with deuterated a subunits was key to this study. Initial modeling efforts having as starting point the crystal structure of homologue PA28 indicate that PA28 heptamer rings are made up of three a and four b subunits in an alternating zig-zag arrangement. The SANS intensities also reveal that there is a well-defined solution equilibrium between heptamer and its double-ring dimer, making the analysis more intricate than anticipated.
M Sugiyama (Kyoto University, Japan), E Kurimoto (Meijo University, Japan), S Takata (JAEA, Japan), K Kato (Okazaki Institute for Integrative Bioscience and Institute for Molecular Science, Japan)
Research date: January 2010
Contact: Dr M Sugiyama, email@example.com
Further reading: M Sugiyama, in preparation