ATPase and ubiquitin-binding proteins of the yeast proteasome.
The 26S proteasome is a 2-Megadalton proteolytic complex with over 30 distinct subunits. The 19S particle, a subcomplex of the 26S proteasome, is thought to confer ATP-dependence and ubiquitin-dependence on the proteolytic core particle of the proteasome. Given the complexity of the 19S particle, genetic approaches are likely to play an important role in its analysis. We have initiated biochemical and genetic studies of the 19S particle in Saccharomyces cerevisiae. Here we describe the localization to the proteasome of several ATPases that were previously proposed to be involved in transcription. Independent studies indicate that the mammalian 26S proteasome contains closely related ATPases. We have also found that the multiubiquitin chain binding protein Mcb1, a homolog of the mammalian S5a protein, is a subunit of the yeast proteasome. However, contrary to expectation, MCB1 is not an essential gene in yeast. The mcb1 mutant grows at a nearly wild-type rate, and the breakdown of most ubiquitin-protein conjugates is unaffected in this strain. One substrate, Ub-Proline-beta gal, was found to require MCB1 for its breakdown, but it remains unclear whether Mcb1 serves as a ubiquitin receptor in this process. Our data suggest that the recognition of ubiquitin conjugates by the proteasome is a complex process which must involve proteins other than Mcb1.
Rubin
D M
DM
Department of Cell Biology, Harvard Medical School, Boston, MA 02146, USA.
van Nocker
S
S
Glickman
M
M
Coux
O
O
Wefes
I
I
Sadis
S
S
Fu
H
H
Goldberg
A
A
Vierstra
R
R
Finley
D
D
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism; D005656:Fungal Proteins / Q000378:metabolism; D005800:Genes, Fungal / Q000502:physiology; D009154:Mutation; D010447:Peptide Hydrolases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex; D011485:Protein Binding; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins
D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C122019:RPN10 protein, S cerevisiae; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D010447:Peptide Hydrolases; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease; D000251:Adenosine Triphosphatases; C084493:RPT1 protein, S cerevisiae; C069670:RPT6 protein, S cerevisiae