期刊
JOURNAL OF BIOLOGICAL CHEMISTRY
卷 285, 期 33, 页码 25554-25569出版社
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.M110.136622
关键词
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资金
- NHGRI [1P50HG004952]
- NIGMS [P01GM081269]
- United States Department of Energy [DE-FG02-88ER13968]
- National Science Foundation Arabidopsis [MCB-0115870]
- U.S. Department of Energy (DOE) [DE-FG02-88ER13968] Funding Source: U.S. Department of Energy (DOE)
Selective proteolysis in plants is largely mediated by the ubiquitin (Ub)/proteasome system in which substrates, marked by the covalent attachment of Ub, are degraded by the 26 S proteasome. The 26 S proteasome is composed of two subparticles, the 20 S core protease (CP) that compartmentalizes the protease active sites and the 19 S regulatory particle that recognizes and translocates appropriate substrates into the CP lumen for breakdown. Here, we describe an affinity method to rapidly purify epitope-tagged 26 S proteasomes intact from Arabidopsis thaliana. In-depth mass spectrometric analyses of preparations generated from young seedlings confirmed that the 2.5-MDa CP-regulatory particle complex is actually a heterogeneous set of particles assembled with paralogous pairs for most subunits. A number of these subunits are modified post-translationally by proteolytic processing, acetylation, and/or ubiquitylation. Several proteasome-associated proteins were also identified that likely assist in complex assembly and regulation. In addition, we detected a particle consisting of the CP capped by the single subunit PA200 activator that may be involved in Ub-independent protein breakdown. Taken together, it appears that a diverse and highly dynamic population of proteasomes is assembled in plants, which may expand the target specificity and functions of intracellular proteolysis.
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