Solution structure of proteasome activators
10 Oct 2010



In biological cells, the so-called ‘20S proteasome’ is responsible for breaking down damaged or unneeded proteins so they can be recycled into new ones.

​​​Sans2d data for PA28 (points) and initial simulations (lines) allowing for dimer–monomer equilibrium. D2O/H2O contrast variation with deuterated a subunits shows that the rings comprise three a and four b units.

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

Further Information

Contact: Dr M Sugiyama,

Further reading: M Sugiyama, in preparation​