期刊
EMBO JOURNAL
卷 27, 期 16, 页码 2204-2213出版社
NATURE PUBLISHING GROUP
DOI: 10.1038/emboj.2008.148
关键词
assembly; chaperone; propeptide; proteasome; ubiquitin
资金
- Ministry of Education, Science and Culture of Japan (MEXT)
- Target Protein Project of MEXT
- Takeda Science Foundation (KT)
The 20S proteasome is the catalytic core of the 26S proteasome. It comprises four stacked rings of seven subunits each, alpha(1-7)beta(1-7)beta(1-7)alpha(1-7). Recent studies indicated that proteasome-specific chaperones and beta-subunit appendages assist in the formation of alpha-rings and dimerization of half-proteasomes, but the process involved in the assembly of beta-rings is poorly understood. Here, we clarify the mechanism of beta- ring formation on alpha-rings by characterizing assembly intermediates accumulated in cells depleted of each beta-subunit. Starting from beta 2, incorporation of beta-subunits occurs in an orderly manner dependent on the propeptides of beta 2 and beta 5, and the C-terminal tail of beta 2. Unexpectedly, hUmp1, a chaperone functioning at the final assembly step, is incorporated as early as beta 2 and is required for the structural integrity of early assembly intermediates. We propose a model in which beta-ring formation is assisted by both intramolecular and extrinsic chaperones, whose roles are partially different between yeast and mammals.
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