科研之友
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摘要
Elevation of polyamine levels in eukaryotes leads to rapid degradation of ornithine decarboxylase (ODC), the first enzyme of polyamine biosynthesis pathway. ODC in yeast (yODC) has two domains, the N alpha/beta domain consisting of alpha/beta barrel domain (alpha/beta) preceded by an overhang of 50 residues at its N-terminus (N50) and beta sheet domain at its C-terminus. Two degradation determinant signals or degrons in yODC sequence, namely the N50 and the antizyme-binding element (AzBE) housed in the alpha/beta domain, are responsible for its degradation by proteasomes. Antizyme (Az) induced under polyamine excess binds to AzBE and delivers ODC to proteasome, while the N50 threads the protein into proteasome. It was previously reported by us that the peptide N alpha/beta of yODC acts as an independent transplantable degron, whose action can be modulated with the help of antizyme by varying polyamine levels. Mammalian ODC (mODC), in spite of its 40% sequence homology with yODC, is devoid of N50 of yODC and instead sports a C-terminal tail of 37 residues (CmODC). CmODC acts as an independent transplantable degron with no equivalent in yODC. The present study investigates the merits of employing the two degrons N alpha/beta and CmODC together for targeted protein degradation by expressing them in a chimeric fusion with green fluorescent protein (GFP). Our results establish that under the regulation of antizyme, the signals N alpha/beta and CmODC acting together enhance degradation better than either degron in isolation. The combination of N alpha/beta and CmODC can be employed to study the function of novel proteins through their rapid removal.
- 出版日期2017-4
