Structural Analysis of the Bacterial Proteasome Activator Bpa in Complex with the 20S Proteasome.

Bolten M; Delley CL; Leibundgut M; Boehringer D; Ban N; Weber-Ban E

doi:10.1016/j.str.2016.10.008

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Structural Analysis of the Bacterial Proteasome Activator Bpa in Complex with the 20S Proteasome.

Bolten M ETH Zurich, Institute of Molecular Biology & Biophysics, 8093 Zurich, Switzerland.
Delley CL ETH Zurich, Institute of Molecular Biology & Biophysics, 8093 Zurich, Switzerland.
Leibundgut M ETH Zurich, Institute of Molecular Biology & Biophysics, 8093 Zurich, Switzerland.
Boehringer D ETH Zurich, Institute of Molecular Biology & Biophysics, 8093 Zurich, Switzerland.
Ban N ETH Zurich, Institute of Molecular Biology & Biophysics, 8093 Zurich, Switzerland.
Weber-Ban E ETH Zurich, Institute of Molecular Biology & Biophysics, 8093 Zurich, Switzerland. Electronic address: eilika@mol.biol.ethz.ch.

2016-11-15

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Structure (London, England : 1993). - 2016

bacterial proteasome activator

Proteasome Endopeptidase Complex

English Mycobacterium tuberculosis harbors proteasomes that recruit substrates for degradation through an ubiquitin-like modification pathway. Recently, a non-ATPase activator termed Bpa (bacterial proteasome activator) was shown to support an alternate proteasomal degradation pathway. Here, we present the cryo-electron microscopy (cryo-EM) structure of Bpa in complex with the 20S core particle (CP). For docking into the cryo-EM density, we solved the X-ray structure of Bpa, showing that it forms tight four-helix bundles arranged into a 12-membered ring with a 40 Å wide central pore and the C-terminal helix of each protomer protruding from the ring. The Bpa model was fitted into the cryo-EM map of the Bpa-CP complex, revealing its architecture and striking symmetry mismatch. The Bpa-CP interface was resolved to 3.5 Å, showing the interactions between the C-terminal GQYL motif of Bpa and the proteasome α-rings. This docking mode is related to the one observed for eukaryotic activators with features specific to the bacterial complex.

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