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EMBO J. 2003 Apr 1;22(7):1488-96.

Determinants of proteasome recognition of ornithine decarboxylase, a ubiquitin-independent substrate.

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  • 1Department of Microbiology and Immunology, University of California, San Francisco, CA 94143, USA.

Abstract

Ornithine decarboxylase (ODC) is regulated by its metabolic products through a feedback loop that employs a second protein, antizyme 1 (AZ1). AZ1 accelerates the degradation of ODC by the proteasome. We used purified components to study the structural elements required for proteasomal recognition of this ubiquitin-independent substrate. Our results demonstrate that AZ1 acts on ODC to enhance the association of ODC with the proteasome, not the rate of its processing. Substrate-linked or free polyubiquitin chains compete for AZ1-stimulated degradation of ODC. ODC-AZ1 is therefore recognized by the same element(s) in the proteasome that mediate recognition of polyubiquitin chains. The 37 C-terminal amino acids of ODC harbor an AZ1-modulated recognition determinant. Within the ODC C terminus, three subsites are functionally distinguishable. The five terminal amino acids (ARINV, residues 457-461) collaborate with residue C441 to constitute one recognition element, and AZ1 collaborates with additional constituents of the ODC C terminus to generate a second recognition element.

PMID:
12660156
[PubMed - indexed for MEDLINE]
PMCID:
PMC152902
Free PMC Article

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