Article
- The EMBO Journal (2007) 26, 123 - 131
- doi:10.1038/sj.emboj.7601476
Published online: 14 December 2006
Subject Categories:
Proteasome substrate degradation requires association plus extended peptide
Junko Takeuchi1, Hui Chen1,a and Philip Coffino1
- Department of Microbiology and Immunology, University of California, San Francisco, CA, USA
Correspondence to:
Philip Coffino, Department of Microbiology and Immunology, University of California, San Francisco, 513 Parnassus Ave, Microbiology room S430, San Francisco, CA 94143, USA. Tel.: +1 415 516 6515; Fax: +1 415 476 8201; E-mail: philip.coffino@ucsf.edu
aPresent address: Department of Biopharmaceutical Sciences, University of California, San Francisco, CA 94143, USA
Received 1 August 2006; Accepted 6 November 2006
Abstract
To determine the minimum requirements for substrate recognition and processing by proteasomes, the functional elements of a ubiquitin-independent degradation tag were dissected. The 37-residue C-terminus of ornithine decarboxylase (cODC) is a native degron, which also functions when appended to diverse proteins. Mutating the cysteine 441 residue within cODC impaired its proteasome association in the context of ornithine decarboxylase and prevented the turnover of GFP-cODC in yeast cells. Degradation of GFP-cODC with C441 mutations was restored by providing an alternate proteasome association element via fusion to the Rpn10 proteasome subunit. However, Rpn10-GFP was stable, unless extended by cODC or other peptides of similar size. In vitro reconstitution experiments confirmed the requirement for both proteasome tethering and a loosely structured region. Therefore, cODC and degradation tags in general must serve two functions: proteasome association and a site, consisting of an extended peptide region, used for initiating insertion into the protease.
Keywords:
- degron,
- ornithine decarboxylase,
- proteasome,
- proteolysis,
- ubiquitin
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