标题：Cloning of a trypanosomatid gene coding for an ornithine decarboxylase that is metabolically unstable even though it lacks the C-terminal degradation domain
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1997
卷号：94
期号：2
页码：397-402
DOI：10.1073/pnas.94.2.397
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Mammalian ornithine decarboxylase (ODC) is among the most labile of cellular proteins, with a half-life of usually less than an hour. Like other short-lived proteins ODC is degraded by the 26S proteasome. Its degradation is not triggered by ubiquitination, but is stimulated by the binding of an inducible protein, antizyme. Truncations and mutations in the C terminus of mammalian ODC have been shown to prevent the rapid turnover of the enzyme, demonstrating the presence of a degradation signal in this region. Moreover, ODCs from the trypanosomatid parasites Trypanosoma brucei and Leishmania donovani, which lack this C-terminal domain, are metabolically stable, and recombination of T. brucei ODC with the C terminus of mammalian ODC confers a short half-life to the fusion protein when expressed in mammalian cells. In the present study we have cloned and sequenced the ODC gene from the trypanosomatid Crithidia fasciculata. To our knowledge, this is the first protozoan shown to have an ODC with a rapid turnover. The sequence analysis revealed a high homology between C. fasciculata ODC and L. donovani ODC, despite the difference in stability. We demonstrate that C. fasciculata ODC has a very rapid turnover even when expressed in mammalian cells. Moreover, ODC from C. fasciculata is shown to lack the C-terminal degradation domain of mammalian ODC. Our findings indicate that C. fasciculata ODC contains unique signals, targeting the enzyme for rapid degradation not only in the parasite but also in mammalian cells.
关键词：Crithidia fasciculata ; protein turnover ; polyamines ; PEST region
