INVIVO HALF-LIFE OF A PROTEIN IS A FUNCTION OF ITS AMINO-TERMINAL RESIDUE
INVIVO HALF-LIFE OF A PROTEIN IS A FUNCTION OF ITS AMINO-TERMINAL RESIDUE
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DOI：
10.1126/science.3018930
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发表时间：
1986-10-10
期刊：
影响因子：
56.9
通讯作者：
VARSHAVSKY, A
中科院分区：
文献类型：
--
作者：
BACHMAIR, A;FINLEY, D;VARSHAVSKY, A
当编码泛素-β-半乳糖苷酶融合蛋白的嵌合基因在酵母（酿酒酵母）中表达时，泛素从新生的融合蛋白中分离出来，产生去泛素化的β-半乳糖苷酶（βgal）。除了一个例外，无论在泛素-β半乳糖连接处的β半乳糖氨基酸残基的性质如何，这种切割都会发生，从而使得在其他相同的β半乳糖蛋白的氨基末端暴露不同的残基成为可能。这样设计的β半乳糖蛋白在体内的半衰期有显著不同，根据β半乳糖氨基端氨基酸的性质，从20多小时到不到3分钟不等。因此，单个氨基酸的集合可以根据它们在β - gal的氨基端存在时赋予β - gal的半衰期进行排序（“n端规则”）。目前已知的原核生物和真核生物的长寿命、非区隔化的细胞内蛋白的氨基末端残基完全属于由n端规则预测的稳定类。前面描述的翻译后将单个氨基酸添加到蛋白质氨基末端的功能也可以用n端规则来解释。因此，识别蛋白质中的氨基末端残基可能介导蛋白质的代谢稳定性和调节其稳定性的潜力。
When a chimeric gene encoding a ubiquitin-β-galactosidase fusion protein is expressed in the yeastSaccharomyces cerevisiae, ubiquitin is cleaved off the nascent fusion protein, yielding a deubiquitinated β-galactosidase (βgal). With one exception, this cleavage takes place regardless of the nature of the amino acid residue of βgal at the ubiquitin-βgal junction, thereby making it possible to expose different residues at the amino-termini of the otherwise identical βgal proteins. The βgal proteins thus designed have strikingly different half-lives in vivo, from more than 20 hours to less than 3 minutes, depending on the nature of the amino acid at the amino-terminus of βgal. The set of individual amino acids can thus be ordered with respect to the half-lives that they confer on βgal when present at its amino-terminus (the "N-end rule"). The currently known amino-terminal residues in long-lived, noncompartmentalized intracellular proteins from both prokaryotes and eukaryotes belong exclusively to the stabilizing class as predicted by the N-end rule. The function of the previously described posttranslational addition of single amino acids to protein amino-termini may also be accounted for by the N-end rule. Thus the recognition of an amino-terminal residue in a protein may mediate both the metabolic stability of the protein and the potential for regulation of its stability.