20S Proteasome Prevents Aggregation of Heat-Denatured Proteins without PA700 Regulatory Subcomplex Like a Molecular Chaperone

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• 作者：Mihiro Yano ; Yasuko Koumoto ; Yukiko Kanesaki ; Xueji Wu ; and Hiroshi Kido
• 刊名：Biomacromolecules
• 出版年：2004
• 出版时间：July 2004
• 年：2004
• 卷：5
• 期：4
• 页码：1465 - 1469
• 全文大小：66K
• 年卷期：v.5,no.4(July 2004)
• ISSN：1526-4602

文摘

The eukaryotic 20S proteasome is the multifunctional catalytic core of the 26S proteasome, which plays acentral role in intracellular protein degradation. Association of the 20S core with a regulatory subcomplex,termed PA700 (also known as the 19S cap), forms the 26S proteasome, which degrades ubiquitinated andnonubiquitinated proteins through an ATP-dependent process. Although proteolytic assistance by thisregulatory particle is a general feature of proteasome-dependent turnover, the 20S proteasome itself candegrade some proteins directly, bypassing ubiquitination and PA700, as an alternative mechanism in vitro.The mechanism underlying this pathway is based on the ability of the 20S proteasome to recognize partiallyunfolded proteins. Here we show that the 20S proteasome recognizes the heat-denatured forms of modelproteins such as citrate synthase, malate dehydrogenase. and glyceraldehydes-3-phosphate dehydrogenase,and prevents their aggregation in vitro. This process was not followed by the refolding of these denaturedsubstrates into their native states, whereas PA700 or the 26S proteasome generally promotes their reactivation.These results indicate that the 20S proteasome might play a role in maintaining denatured and misfoldedsubstrates in a soluble state, thereby facilitating their refolding or degradation.