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In vitro study of proteolytic degradation of rat histidine decarboxylase

Olmo, María T., Urdiales, José L., Pegg, Anthony E., Medina, Miguel A., Sánchez‐Jiménez, Francisca
European journal of biochemistry 2000 v.267 no.5 pp. 1527-1531
histidine decarboxylase, in vitro studies, ornithine decarboxylase, proteasome endopeptidase complex, protein degradation, proteolysis, rats, regulatory proteins
Mammalian ornithine decarboxylase (ODC) is a very unstable protein which is degraded in an ATP‐dependent manner by proteasome 26S, after making contact with the regulatory protein antizyme. PEST regions are sequences described as signals for protein degradation. The C‐terminal PEST region of mammalian ODC is essential for its degradation by proteasome 26S. Mammalian histidine decarboxylase (HDC) is also a short‐lived protein. The full primary sequence of mammalian HDC contains PEST‐regions at both the N‐ and C‐termini. Rat ODC and different truncated and full versions of rat HDC were expressed in vitro. In vitro degradation of rat ODC and rat 1–512 HDC were compared. Like ODC, rat 1–512 HDC is degraded mainly by an ATP‐dependent mechanism. However, antizyme has no effect on the degradation of 1–512 HDC. The use of the inhibitors MG‐132 and lactacystine significantly inhibited the degradation of 1–512 HDC, suggesting that a ubiquitin‐dependent, proteasome 26S proteolytic pathway is involved. Results obtained with the different modifications of rat HDC containing all three PEST regions (full version, 1–656 HDC), only the N‐terminal PEST region (1–512 HDC), or no PEST region (69–512 HDC), indicate that the N‐terminal (1–69) fragment, but not the C‐terminal fragment, determines that the HDC protein is a proteasome substrate in vitro.