Plasticity in eucaryotic 20S proteasome ring assembly revealed by a subunit deletion in yeast

The 20S proteasome is made up of four stacked heptameric rings, which in eucaryotes assemble from 14 different but related subunits. The rules governing subunit assembly and placement are not understood. We show that a different kind of proteasome forms in yeast when the Pre9/α3 subunit is deleted....

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Bibliographic Details
Published in:The EMBO journal 2004-02, Vol.23 (3), p.500-510
Main Authors: Velichutina, Irina, Connerly, Pamela L, Arendt, Cassandra S, Li, Xia, Hochstrasser, Mark
Format: Article
Language:English
Subjects:
Arabidopsis - enzymology
Arabidopsis - genetics
Arabidopsis Proteins - genetics
Arabidopsis Proteins - metabolism
EMBO31
EMBO40
Gene Deletion
Genetic Complementation Test
plasticity
Pre6 gene
pre6 protein
Pre9 gene
pre9 protein
proteasome
Proteasome Endopeptidase Complex - genetics
Proteasome Endopeptidase Complex - metabolism
proteasomes
protein assembly
Protein Subunits - genetics
Protein Subunits - metabolism
proteolysis
Saccharomyces cerevisiae - enzymology
Saccharomyces cerevisiae - genetics
Saccharomyces cerevisiae Proteins - genetics
Saccharomyces cerevisiae Proteins - metabolism
ubiquitin
Yeasts
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Summary:The 20S proteasome is made up of four stacked heptameric rings, which in eucaryotes assemble from 14 different but related subunits. The rules governing subunit assembly and placement are not understood. We show that a different kind of proteasome forms in yeast when the Pre9/α3 subunit is deleted. Purified pre9Δ proteasomes show a two‐fold enrichment for the Pre6/α4 subunit, consistent with the presence of an extra copy of Pre6 in each outer ring. Based on disulfide engineering and structure‐guided suppressor analyses, Pre6 takes the position normally occupied by Pre9, a substitution that depends on a network of intersubunit salt bridges. When Arabidopsis PAD1/α4 is expressed in yeast, it complements not only pre6 Δ but also pre6 Δ pre9 Δ mutants; therefore, the plant α4 subunit also can occupy multiple positions in a functional yeast proteasome. Importantly, biogenesis of proteasomes is delayed at an early stage in pre9 Δ cells, suggesting an advantage for Pre9 over Pre6 incorporation at the α3 position that facilitates correct assembly.
ISSN:0261-4189
1460-2075
DOI:10.1038/sj.emboj.7600059