title: ATP-Dependent inactivation and sequestration of ornithine decarboxylase by the 26S proteasome are prerequisites for degradation.
abstract: The 26S proteasome is a eukaryotic ATP-dependent protease, but the molecular basis of its energy requirement is largely unknown. Ornithine decarboxylase (ODC) is the only known enzyme to be degraded by the 26S proteasome without ubiquitinylation. We report here that the 26S proteasome is responsible for the irreversible inactivation coupled to sequestration of ODC, a process requiring ATP and antizyme (AZ) but not proteolytic activity. Neither the 20S proteasome (catalytic core) nor PA700 (the regulatory complex) by itself contributed to this ODC inactivation. Analysis with a C-terminal mutant ODC revealed that the 26S proteasome recognizes the C-terminal degradation signal of ODC exposed by attachment of AZ, and subsequent ATP-dependent sequestration of ODC in the 26S proteasome causes irreversible inactivation, possibly unfolding, of ODC and dissociation of AZ. These processes may be linked to the translocation of ODC into the 20S proteasomal inner cavity, centralized within the 26S proteasome, for degradation.
authors.affiliation: Department of Biochemistry 2, Jikei University School of Medicine, Minato-ku, Tokyo 105-8461, Japan. yasukomu@jikei.ac.jp
authors.forename: Y
authors.initials: Y
authors.lastname: Murakami
authors.forename: S
authors.initials: S
authors.lastname: Matsufuji
authors.forename: S I
authors.initials: SI
authors.lastname: Hayashi
authors.forename: N
authors.initials: N
authors.lastname: Tanahashi
authors.forename: K
authors.initials: K
authors.lastname: Tanaka
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D003546:Cysteine Endopeptidases; D007783:Lactones / Q000494:pharmacology; D008954:Models, Biological; D009097:Multienzyme Complexes; D009955:Ornithine Decarboxylase / Q000378:metabolism*; D065108:Ornithine Decarboxylase Inhibitors; D010447:Peptide Hydrolases / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex; D011485:Protein Binding; D011506:Proteins / Q000494:pharmacology
chemical_list: D007783:Lactones; D009097:Multienzyme Complexes; D065108:Ornithine Decarboxylase Inhibitors; C085834:PA700 proteasome activator; D011506:Proteins; C031017:ornithine decarboxylase antizyme; C098869:clasto-lactacystin beta-lactone; D000255:Adenosine Triphosphate; D010447:Peptide Hydrolases; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease; D009955:Ornithine Decarboxylase