Ornithine decarboxylase stability in HMOA and DH23b cells is not due to post-translational truncation of a C-terminal recognition site.
Ornithine decarboxylase stability in HMOA and DH23b cells is not due to post-translational truncation of a C-terminal recognition site.
复制标题
鸟氨酸脱羧酶在 HMOA 和 DH23b 细胞中的稳定性不是由于 C 端识别位点的翻译后截短造成的。
DOI：
10.1042/bj3180879
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
Judd,GG
中科院分区：
文献类型：
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作者：
Mitchell,JL;Choe,CY;Judd,GG
在变异细胞系HMOA和DH23b中，当Cys-441被Trp取代时，通常不稳定的鸟氨酸脱羧酶(ODC)变得异常稳定。这种稳定的ODC在SDS/PAGE上也有较高的迁移率。由于以前的研究表明，当从ODC的C-末端去除5个氨基酸残基时，ODC的稳定性就可以实现，因此有人认为，变异体ODC中的氨基酸取代可能会充分改变其构象，从而促进C-端降解信号的类似蛋白水解性丢失，从而产生稳定但活性高的ODC。为了研究这一机制，用羧肽酶-Y消化的方法释放了野生型和稳定型(Trp-441)ODC蛋白C-末端的氨基酸，并用高效液相色谱法对其进行了鉴定。C-末端被发现是相同的，并与从cDNA序列预测的相同。这项研究证明，Trp-441形式的ODC的稳定性不仅仅是由于蛋白水解性去除了C-末端的蛋白酶体靶向序列，从而意味着这种突变的ODC形式的稳定必须直接源于与Cys-441丢失相关的构象变化。
The normally labile ornithine decarboxylase (ODC) becomes unusually stable when Cys-441 is replaced with Trp in the variant cell lines HMOA and DH23b. This stable ODC is also observed to have higher mobility on SDS/PAGE. Because previous studies have shown that ODC stability can be achieved when as few as five amino acid residues are removed from its C-terminus, it was suggested that the amino acid substitution in the variant ODC might alter its conformation sufficiently to promote a similar proteolytic loss of a C-terminal degradation signal, resulting in a stable yet active ODC. To examine this mechanism, amino acids in the C-terminal regions of both wild-type and stable (Trp-441) ODC proteins were released, by means of carboxypeptidase-Y digestion, and identified by HPLC. The C-terminal ends were found to be the same, and are as predicted from the cDNA sequence. This study proves that stability of the Trp-441 form of ODC is not simply due to proteolytic removal of a C-terminal proteasome-targeting sequence, thereby implying that the stabilization of this mutant ODC form must result directly from a conformational change associated with the loss of Cys-441.