Sequence determinants for regulated degradation of yeast 3-hydroxy-3-methylglutaryl-CoA reductase, an integral endoplasmic reticulum membrane protein
Sequence determinants for regulated degradation of yeast 3-hydroxy-3-methylglutaryl-CoA reductase, an integral endoplasmic reticulum membrane protein
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DOI：
10.1091/mbc.9.9.2611
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发表时间：
1998-09-01
影响因子：
3.3
通讯作者：
Hampton, R
中科院分区：
文献类型：
--
作者：
Gardner, R;Cronin, S;Hampton, R
甲氧丙戊酸途径的关键酶3-羟基-3-甲基戊二酰辅酶A还原酶(HMG-R)的降解速率受甲氧戊酸途径的反馈调节。为了发现参与酵母HMG-R同工酶Hmg2p调节降解的内在决定因素，我们用另一个稳定的酵母HMG-R同工酶Hmg1p的相应区域替换了Hmg2p跨膜域的小区域。当Hmg2p的前26个氨基酸被Hmg1p的相同区域取代时，Hmg2p是稳定的。该突变体的稳定性不是由于错误的定位，而是由于无法被识别为降解。当Hmg2p的27-54位氨基酸被替换为Hmg1p的氨基酸残基时，突变株仍被降解，但其降解速率调节较差。该突变体的降解仍然依赖于前26个氨基酸残基和HRD基因的功能。这些突变体表现出泛素化水平的改变，这与它们的降解表型有很好的相关性。这两个决定因素都不足以给予Hmg1p受调控的降解。这些研究提供的证据表明，Hmg2p中存在降解和最佳调控所必需的序列决定因素，并且Hmg2p的降解及其调控可能涉及独立的过程。
The degradation rate of 3-hydroxy-3-methylglutaryl CoA reductase (HMG-R), a key enzyme of the mevalonate pathway, is regulated through a feedback mechanism by the mevalonate pathway. To discover the intrinsic determinants involved in the regulated degradation of the yeast HMG-R isozyme Hmg2p, we replaced small regions of the Hmg2p transmembrane domain with the corresponding regions from the other, stable yeast HMG-R isozyme Hmg1p. When the first 26 amino acids of Hmg2p were replaced with the same region from Hmg1p, Hmg2p was stabilized. The stability of this mutant was not due to mislocalization, but rather to an inability to be recognized for degradation. When amino acid residues 27-54 of Hmg2p were replaced with those from Hmg1p, the mutant was still degraded, but its degradation rate was poorly regulated. The degradation of this mutant was still dependent on the first 26 amino acid residues and on the function of the HRD genes. These mutants showed altered ubiquitination levels that were well correlated with their degradative phenotypes. Neither determinant was sufficient to impart regulated degradation to Hmg1p. These studies provide evidence that there are sequence determinants in Hmg2p necessary for degradation and optimal regulation, and that independent processes may be involved in Hmg2p degradation and its regulation.