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The multicatalytic proteinase complex (proteasome): structure and conformational changes associated with changes in
H Djaballah1, A J Rowe, S E Harding
1Department of Biochemistry, University of Leicester, U.K.
The Biochemical Journal
|June 15, 1993
Summary
The proteasome, a key cellular protein complex, has a revised hollow cylindrical structure. Its activity is modulated by conformational changes, influencing its function and breakdown.
Area of Science:
- Biochemistry
- Cell Biology
- Structural Biology
Background:
- The proteasome is a large protein complex essential for protein degradation in eukaryotic cells.
- Previous models suggested a different structure for the rat liver proteasome.
Purpose of the Study:
- To elucidate the structural details of the multicatalytic proteinase complex (proteasome).
- To investigate conformational changes in the proteasome upon interaction with effectors and during dissociation.
Main Methods:
- Negative stain electron microscopy was used to determine the proteasome's shape and subunit arrangement.
- Sedimentation velocity analysis and dynamic light scattering measured conformational changes and dissociation intermediates.
Main Results:
- A hollow cylindrical proteasome structure with pseudo-helical subunit arrangement was proposed, differing from prior models.
- Direct evidence for proteasome conformational changes was observed, correlating with altered proteolytic activity (e.g., with MnCl2).
- Proteasome dissociation by urea, guanidinium chloride, or low pH led to inactivation, with evidence of intermediate formation.
Conclusions:
- Proteasome structure and function are closely linked, with conformational changes mediating activity modulation.
- The study provides a refined structural model and insights into proteasome regulation mechanisms.