Philip Coffino

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Proteins that are degraded by the proteasome are first modified by a set of enzymes that attach multiple copies of ubiquitin to substrate lysines, but a tiny minority, including the polyamine-synthesizing enzyme ornithine decarboxylase, is handled differently. This enzyme is targeted for destruction by another protein--antizyme. Why does ornithine(More)
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(More)
BACKGROUND Pyridoxal-5'-phosphate (PLP) dependent enzymes catalyze a broad range of reactions, resulting in bond cleavage at C alpha, C beta, or C gamma carbons of D and L amino acid substrates. Ornithine decarboxylase (ODC) is a PLP-dependent enzyme that controls a critical step in the biosynthesis of polyamines, small organic polycations whose controlled(More)
Intracellular degradation of vertebrate ornithine decarboxylase (ODC) is accelerated by polyamines, the products of the pathway controlled by ODC. Antizyme, a reversible, tightly binding protein inhibitor of ODC activity, is believed to be involved in this process. Mouse and Trypanosoma brucei ODCs are structurally similar, but the trypanosome enzyme,(More)
The mechanism of protein quality control and elimination of misfolded proteins in the cytoplasm is poorly understood. We studied the involvement of cytoplasmic factors required for degradation of two endoplasmic reticulum (ER)-import-defective mutated derivatives of carboxypeptidase yscY (DeltassCPY* and DeltassCPY*-GFP) and also examined the requirements(More)
Ornithine decarboxylase (ODC) is among the small set of proteasome substrates that is not ubiquitinated. It is instead degraded in conjunction with the protein antizyme (AZ). ODC and AZ are participants in a regulatory circuit that restricts pools of polyamines, the downstream products of ODC enzymatic activity. Functional studies using directed mutagenesis(More)
The proteasomal ATPase ring, comprising Rpt1-Rpt6, associates with the heptameric α-ring of the proteasome core particle (CP) in the mature proteasome, with the Rpt carboxy-terminal tails inserting into pockets of the α-ring. Rpt ring assembly is mediated by four chaperones, each binding a distinct Rpt subunit. Here we report that the base subassembly of(More)
Ornithine decarboxylase (ODC) was converted from a protein with a short intracellular half-life in mammalian cells to a stable protein by truncating 37 residues at its carboxyl terminus. Cells expressing wild-type protein lost ODC activity with a half-life of approximately 1 hour. Cells expressing the truncated protein, however, retained full activity for(More)
Mouse ODC (ornithine decarboxylase) is quickly degraded by the 26S proteasome in mammalian and fungal cells. Its degradation is independent of ubiquitin but requires a degradation signal composed of residues 425-461 at the ODC C-terminus, cODC (the last 37 amino acids of the ODC C-terminus). Mutational analysis of cODC revealed the presence of two essential(More)
The antizyme family consists of closely homologous proteins believed to regulate cellular polyamine pools. Antizyme1, the first described, negatively regulates ornithine decarboxylase, the initial enzyme in the biosynthetic pathway for polyamines. Antizyme1 targets ornithine decarboxylase for degradation and inhibits polyamine transport into cells, thereby(More)