Substrate size selectivity of 20S proteasomes: analysis with variable-sized synthetic substrates.
Substrate size selectivity of 20S proteasomes: analysis with variable-sized synthetic substrates.
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20S 蛋白酶体的底物尺寸选择性：使用可变尺寸的合成底物进行分析。
DOI：
10.1023/a:1019990201364
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发表时间：
2002
期刊：
影响因子：
--
通讯作者：
Murthy,Jay
中科院分区：
文献类型：
--
作者：
Hortin,GlenL;Murthy,Jay
蛋白酶体是在其内腔表面上具有蛋白水解活性的管状复合物，使得大的底物应该在空间上被阻止到达催化位点。在这里，我们研究底物大小对20 S蛋白酶体ofMethanosarcina thermophila裂解率的影响。通过将恒定底物基团（Ala-Ala-Phe-p-nitroanilide）连接到具有可变链长的线性聚合物（甲氧基聚乙二醇）来制备可变大小的合成显色底物。最小的大分子底物比游离三肽底物更有效地裂解，并且大分子底物的裂解是可饱和的，而游离三肽底物的裂解不是，表明大底物和小底物的裂解之间的机理差异。大分子底物裂解的速率逐渐降低高达10倍，作为基板的聚合物组分的大小增加。大分子合成底物似乎是蛋白酶体对天然蛋白质底物作用的更好模型，并证明了蛋白酶体的底物大小选择性。
Proteasomes are tubular complexes with proteolytic activities on their lumenal surfaces so that large substrates should be sterically hindered from reaching the catalytic sites. Here we examine effects of substrate size on rates of cleavage by 20S proteasomes ofMethanosarcina thermophila. Synthetic chromogenic substrates of variable size were prepared by linking a constant substrate group (Ala-Ala-Phe-p-nitroanilide) to a linear polymer (methoxypolyethylene glycol) with variable chain length. The smallest macromolecular substrates were cleaved more efficiently than free tripeptide substrate, and cleavage of macromolecular substrates was saturable, whereas cleavage of free tripeptide substrate was not, indicating mechanistic differences between the cleavage of large and small substrates. Rates of macromolecular substrate cleavage decreased progressively up to 10-fold as the size of the polymeric component of substrates increased. Macromolecular synthetic substrates appear to be better models of proteasome action on natural protein substrates and demonstrate substrate size selectivity of proteasomes.