| Summary: | Protein degradation is essential for maintaining cellular homeostasis. The proteasome is the centralenzyme responsible for non-lysosomal protein degradation in eukaryotic cells. Although proteasome assembly is not yet completelyunderstood, a number of cofactors required for proper assembly and maturation have been identified. Ump1 is a short-livedmaturation factor required for the efficient biogenesis of the 20S proteasome. Upon the association of the two precursorcomplexes, Ump1 is encased and is rapidly degraded after the proteolytic sites in the interior of the nascent proteasome areactivated. In order to further understand the mechanisms behind proteasomal maturation, we expressed and purified yeast Ump1 inE. coli for biophysical and structural analysis.
We show that recombinant Ump1 is purified as a mixture of different oligomeric species and thatoligomerization is mediated by intermolecular disulfide bond formation involving the only cysteine residue present in the protein.Furthermore, a combination of bioinformatic, biochemical and structural analysis revealed that Ump1 shows characteristics of anintrinsically disordered protein, which might become structured only upon interaction with the proteasomesubunits.
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