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Molecular mechanism for degradation of ornithine decarboxylase by 26 S proteasome

26S蛋白酶体降解鸟氨酸脱羧酶的分子机制

基本信息

批准号：
05670132
负责人：
MURAKAMI Yasuko
金额：
$ 1.34万
依托单位：
The Jikei University school of Medicine
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1994
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-05670132/
关键词：
ornithine decarboxylase antizyme proteolysis proteasome protein degrdtion regulation polyamine

项目摘要

Ornithine decarboxylase (ODC), one of the most unstable protein, is ATP-dependently degraded by the 26S proteasome without ubiquitination. The degradation is dependent on antizyme, a polyamine-induced protein that binds to ODC,inhibiting its activity. The present study aimed to understand molecular mechanism whereby 26 S proteasome recognizes and degrades ODC-antizyme complex. First, we examined the role of antizyme by (1) spectrophotometric analysis of the structural changes of ODC caused by binding with antizyme, (2) analysis of functional regions of antizyme and analysis of degradation of mutant ODC.Second, we examined the site of ODC recognized by 26 S proteasome by (1) analysis of degradation products of ODC,(2) analysis of inhibitory effects of various synthetic peptides, each simulating different part of ODC sequence, on ODC degradation, and (3) identification of the enzyme which catalyses constitutive ODC degradation. The results suggested that antizyme binds to ODC monomer and inactivates it with C-terminal half (122-218) and elicits a conformational change of ODC with an adjacent region (113-118), resulting in exposure of a hidden degradation signal of ODC to 26 S proteasome. The multicatalytic proteinase was seemed to cleave ODC at many sites (mainly carboxyl sides of neutral/hydrophobic amino acid residues) by its endoproteolytic function, generating oligopeptides consisting of 5-11 amino acid residues. Antizyme was not degraded during ODC degradation. It was suggested that antizyme does not carry degradation signal within its molecule but accelerates constitutive ODC degradation, also catalyzed by the 26 S proteasome, by enhancing the association of ODC to proteinase. The degradation signal of ODC remained to be clarified by future work.

鸟氨酸脱羧酶(ODC)是最不稳定的蛋白质之一，在没有泛素化的情况下被26S蛋白酶体依赖于ATP降解。降解依赖于抗酶，抗酶是一种多胺诱导的蛋白质，它与ODC结合，抑制其活性。本研究旨在了解26 S蛋白酶体识别和降解ODC型抗酶复合体的分子机制。首先，我们通过(1)抗酶结合引起的ODc结构变化的分光光度分析，(2)抗酶功能区的分析和突变型ODC的降解分析，首先通过(1)ODc降解产物的分析，(2)各种模拟ODc序列不同部分的合成肽对ODc降解的抑制作用的分析，(3)催化组成ODc降解的酶的鉴定，检测了26个S蛋白酶体识别的ODc的位置。结果表明，抗酶可与ODC型单体结合，使其C末端部分(12 2~2 18)失活，引起ODC113~118位的构象变化，从而使ODC2 6 S蛋白酶体暴露出一个隐藏的降解信号。多催化蛋白水解酶通过其内切作用在许多位置(主要是中性/疏水氨基酸残基的羧基)裂解ODC，产生由5-11个氨基酸残基组成的寡肽。在ODC降解过程中，不降解抗酶。结果表明，抗酶并不携带降解信号，而是通过增强胞外基质与蛋白酶的结合来加速胞外基质的结构性降解，该降解同样由26 S蛋白酶体催化。ODC的降解信号有待于下一步工作的澄清。