A unified pathway for the degradation of ornithine decarboxylase in reticulocyte lysate requires interaction with the polyamine-induced protein, ornithine decarboxylase antizyme.
Recent studies have provided convincing evidence to add to a number of earlier observations suggesting that the rapid intracellular degradation of mammalian ornithine decarboxylase (ODC) is further accelerated by the action of ornithine decarboxylase antizyme (ODC-Az), a polyamine-induced protein. However, the mechanism whereby ODC-Az exerts its effect in this proteolytic process is mostly unknown. Here, by using reticulocyte-lysate-based synthesis and degradation systems, we demonstrate that interaction of ODC-Az with ODC results in two related outcomes: (a) ODC is inactivated as a result of its monomerization, and (b) ODC degradation is dramatically accelerated. While ODC inactivation requires the integrity of the ODC-Az binding site of ODC and the ODC binding site of ODC-Az, acceleration in ODC degradation also requires the previously characterized carboxyl-terminal destabilizing segment of ODC and a specific segment of ODC-Az that may be functionally distinct from that required for ODC binding. Interestingly, an active ODC variant with a mutant ODC-Az binding site is stable under basal degradation conditions. This, together with the ability of anti-(ODC-Az) antibody to specifically inhibit the basal degradation of ODC in the lysate, suggests that ODC-Az is an essential general mediator of ODC degradation. Based on these observations, we propose a model for the degradation of ODC which always require interaction with antizyme.
Mamroud-Kidron
E
E
Department of Molecular Genetics and Virology, Weizmann Institute of Science, Rehovot, Israel.
Omer-Itsicovich
M
M
Bercovich
Z
Z
Tobias
K E
KE
Rom
E
E
Kahana
C
C
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D046911:Macromolecular Substances; D051379:Mice; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009955:Ornithine Decarboxylase / Q000737:chemistry / Q000378:metabolism*; D065108:Ornithine Decarboxylase Inhibitors; D017354:Point Mutation; D011073:Polyamines / Q000494:pharmacology*; D011506:Proteins / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D012156:Reticulocytes / Q000201:enzymology*; D013329:Structure-Activity Relationship
D046911:Macromolecular Substances; D065108:Ornithine Decarboxylase Inhibitors; D011073:Polyamines; D011506:Proteins; C031017:ornithine decarboxylase antizyme; D009955:Ornithine Decarboxylase