1P-36 PDF
Native mass spectrometric analysis for the oligomeric state of proteasome α7 subunit
Native mass spectrometry is the method that enables molecular mass measurements of proteins under non-denaturing conditions. Therefore native mass spectrometry can be a powerful tool to characterize non-covalently associated oligomeric states of protein complexes. The proteasome is a huge oligomeric protein complex and has a protein-degradation activity against ubiquitin-tagged proteins. The assembly mechanisms of the proteasome remain to be solved. Our research aim is to clarify the dynamic assembly process of the proteasome complex. It has been known that the 20S core particle is composed of two α-rings and two β-rings. In the mature proteasome, α-ring is constituted from 7 types of subunits, α1-α7. Whereas, our solution scattering data showed that the α7 spontaneously forms homotetradecamer that assumes a double-ring structure composed of two heptameric rings. In this study, we applied native mass spectrometry to analyze the oligomeric state of α7. We successfully obtained mass spectrum of α7 oligomer. The determined mass (408,587 Da) of the α7 oligomer clearly indicates the stable formation of α7 tetradecamer. We also identified an α7 homoheptamer with a molecular mass of 192,530 Da. These results are consistent with the solution scattering observation that tetradecameric α7 double-ring was composed of two heptameric rings.