Department of Molecular Structural Biology, Max Planck Institute of Biochemistry（Project Group leader）
|世話人||田中 啓二 （東京都医学総合研究所 所長）|
26S proteasome is a 2.5 MDa protein complex that is composed of a catalytic 20S core particle (CP) and 19S regulatory particles (RPs) containing hexameric AAA+ ATPase ring. Entry of the substrates into the CP is regulated by N-termini of α subunits. However, the fundamental mechanism by which the RP controls the CP gate-opening remains unclear. We sought to understand the gate-opening mechanism and analyzed structures of the 26S proteasome by single-particle cryo-electron microscopy (cryo-EM). Addition of different nucleotide analogs led us to identify several novel conformations in which the CP gate is open. High resolution open-gate structures help to understand how the proteasome gate is regulated by the AAA+ ATPases. In addition to the HbYX-motif insertions, engagement of the C-termini of Rpt1 and Rpt6 are necessary to open the CP gate. These insertions induce the conformational change of α2 and α4 subunits, resulting in the rearrangement of the N-termini of α subunits.