Structural analysis of the 26S proteasome by cryoelectron microscopy

Stephan Nickell, Oana Mihalache, Florian Beck, Reiner Hegerl, Andreas Korinek and Wolfgang Baumeister

The 26S proteasome is the key enzyme of intracellular protein degradation in eukaryotic cells. It is a multisubunit complex of 2.5 MDa confining the proteolytic action to an inner compartment with tightly controlled access. Structural studies of this intriguing molecular machine have been hampered by its intrinsic instability and its dynamics. We have used an unconventional approach to obtain a three-dimensional structure of the holocomplex uncompromised by preparation-induced alterations and unbiased by any starting model.
Now the goal is to refine this first model of the 26S proteasome by a single particle approach using
high-throughput electron microscopy and the Spider program package for image processing.