Length of the active-site crossover loop defines the substrate specificity of ubiquitin C-terminal hydrolases for ubiquitin chains
Length of the active-site crossover loop defines the substrate specificity of ubiquitin C-terminal hydrolases for ubiquitin chains
复制标题
活性位点交叉环的长度定义了泛素 C 末端水解酶对泛素链的底物特异性。
DOI：
10.1042/bj20110699
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发表时间：
2012-01-01
影响因子：
4.1
通讯作者：
Hu, Hong-Yu
中科院分区：
文献类型：
--
作者：
Zhou, Zi-Ren;Zhang, Yu-Hang;Hu, Hong-Yu
UCH [Ub（泛素）C 端水解酶] 是一个去泛素化酶家族，通常被认为只能从 Ub 加合物中去除小的 C 端肽尾。在迄今为止确定的四种 UCH 中，UCH-L3 和 UCH-L1 都不能催化异肽 Ub 链的水解，但当 UCH-L5 存在于蛋白酶体的 PA700 复合物中时可以。在本文中，我们报道了UCH-L5的UCH结构域，与UCH-L1和UCH-L3不同，其本身可以通过裂解两个Ub单元之间的异肽键来加工K48-diUb（Lys48连接的双泛素）底物。四个 UCH 的催化特异性取决于活性位点交叉环的长度。具有长交叉环（通常 > 14 个残基）的 UCH 结构域，例如 UCH-L5 或 BAP1 [BRCA1（乳腺癌早发 1）相关蛋白 1] 的 UCH 结构域，能够裂解小型和大型 Ub 衍生物，而具有短环的 UCH 结构域只能处理小型 Ub 衍生物。我们还发现，交叉环的延长使得UCH-L1能够以长度依赖性方式对K48-diUb具有肽酶活性。因此，UCH 的环长度决定了它们对 diUb 链的底物特异性，表明交叉环的链灵活性在决定其切割异肽 Ub 链的催化活性和底物特异性方面起着重要作用。
UCHs [Ub (ubiquitin) C-terminal hydrolases] are a family of deubiquitinating enzymes that are often thought to only remove small C-terminal peptide tails from Ub adducts. Among the four UCHs identified to date, neither UCH-L3 nor UCH-L1 can catalyse the hydrolysis of isopeptide Ub chains, but UCH-L5 can when it is present in the PA700 complex of the proteasome. In the present paper, we report that the UCH domain of UCH-L5, different from UCH-L1 and UCH-L3, by itself can process the K48-diUb (Lys48-linked di-ubiquitin) substrate by cleaving the isopeptide bond between two Ub units. The catalytic specificity of the four UCHs is dependent on the length of the active-site crossover loop. The UCH domain with a long crossover loop (usually >14 residues), such as that of UCH-L5 or BAP1 [BRCA1 (breast cancer early-onset 1)-associated protein 1], is able to cleave both small and large Ub derivatives, whereas the one with a short loop can only process small Ub derivatives. We also found that elongation of the crossover loop enables UCH-L1 to have isopeptidase activity for K48-diUb in a length-dependent manner. Thus the loop length of UCHs defines their substrate specificity for diUb chains, suggesting that the chain flexibility of the crossover loop plays an important role in determining its catalytic activity and substrate specificity for cleaving isopeptide Ub chains.