期刊
EMBO JOURNAL
卷 19, 期 1, 页码 94-102出版社
OXFORD UNIV PRESS
DOI: 10.1093/emboj/19.1.94
关键词
chaperone; polyubiquitin; 26S proteasome; ubiquitin
资金
- NCI NIH HHS [T32CA09110] Funding Source: Medline
- NIDDK NIH HHS [DK46984] Funding Source: Medline
- NIGMS NIH HHS [GM37009] Funding Source: Medline
Polyubiquitin chains linked through Lys48 are the principal signal for targeting substrates to the 26S proteasome. Through studies of structurally defined, polyubiquitylated model substrates, we show that tetra-ubiquitin is the minimum signal for efficient proteasomal targeting. The mechanism of targeting involves a simple increase in substrate affinity that is brought about by autonomous binding of the polyubiquitin chain. Assigning the proteasomal signaling function to a specific polymeric unit explains how a single ubiquitin can act as a functionally distinct signal, for example in endocytosis. The properties of the substrates studied here implicate substrate unfolding as a kinetically dominant step in the proteolysis of properly folded proteins, and suggest that extraproteasomal chaperones are required for efficient degradation of certain proteasome substrates.
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