Polyubiquitin substrates allosterically activate their own degradation by the 26S proteasome.
The 26S proteasome degrades polyubiquitylated (polyUb) proteins by an ATP-dependent mechanism. Here we show that binding of model polyUb substrates to the 19S regulator of mammalian and yeast 26S proteasomes enhances the peptidase activities of the 20S proteasome about two-fold in a process requiring ATP hydrolysis. Monoubiquitylated proteins or tetraubiquitin alone exert no effect. However, 26S proteasomes from the yeast alpha3DeltaN open-gate mutant and the rpt2YA and rpt5YA mutants with impaired gating can still be activated (approximately 1.3-fold to 1.8-fold) by polyUb-protein binding. Thus, binding of polyUb substrates to the 19S regulator stabilizes gate opening of the 20S proteasome and induces conformational changes of the 20S proteasome that facilitate channeling of substrates and their access to active sites. In consequence, polyUb substrates will allosterically stimulate their own degradation.
Bech-Otschir
Dawadschargal
D
Institut für Biochemie, Charité-Universitätsmedizin Berlin, Monbijoustrasse 2, 10117 Berlin, Germany.
Helfrich
Annett
A
Enenkel
Cordula
C
Consiglieri
Gesa
G
Seeger
Michael
M
Holzhütter
Hermann-Georg
HG
Dahlmann
Burkhardt
B
Kloetzel
Peter-Michael
PM
D018360:Crystallography, X-Ray; D006801:Humans; D018396:Mucin-1 / Q000378:metabolism; D025821:Polyubiquitin / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000378:metabolism
C060192:MUC1 protein, human; D018396:Mucin-1; D025821:Polyubiquitin; D046988:Proteasome Endopeptidase Complex