Multiple associated proteins regulate proteasome structure and function.
We have identified proteins that are abundant in affinity-purified proteasomes, but absent from proteasomes as previously defined because elevated salt concentrations dissociate them during purification. The major components are a deubiquitinating enzyme (Ubp6), a ubiquitin-ligase (Hul5), and an uncharacterized protein (Ecm29). Ecm29 tethers the proteasome core particle to the regulatory particle. Proteasome binding activates Ubp6 300-fold and is mediated by the ubiquitin-like domain of Ubp6, which is required for function in vivo. Ubp6 recognizes the proteasome base and its subunit Rpn1, suggesting that proteasome binding positions Ubp6 proximally to the substrate translocation channel. ubp6Delta mutants exhibit accelerated turnover of ubiquitin, indicating that deubiquitination events catalyzed by Ubp6 prevent translocation of ubiquitin into the proteolytic core particle.
Leggett
David S
DS
Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA.
Hanna
John
J
Borodovsky
Anna
A
Crosas
Bernat
B
Schmidt
Marion
M
Baker
Rohan T
RT
Walz
Thomas
T
Ploegh
Hidde
H
Finley
Daniel
D
D000255:Adenosine Triphosphate / Q000378:metabolism; D001665:Binding Sites; D002172:Canavanine / Q000378:metabolism; D003546:Cysteine Endopeptidases / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism* / Q000648:ultrastructure; D010450:Endopeptidases / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D008025:Ligases / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D009097:Multienzyme Complexes / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism* / Q000648:ultrastructure; D046988:Proteasome Endopeptidase Complex; D011485:Protein Binding; D021122:Protein Subunits / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D012492:Salts / Q000737:chemistry; D044767:Ubiquitin-Protein Ligases
D009097:Multienzyme Complexes; C085834:PA700 proteasome activator; D021122:Protein Subunits; D011506:Proteins; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D012492:Salts; D002172:Canavanine; D000255:Adenosine Triphosphate; C468547:HUL5 protein, S cerevisiae; D044767:Ubiquitin-Protein Ligases; D010450:Endopeptidases; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; C109028:UBP6 protein, S cerevisiae; D008025:Ligases