Yan N, Doelling J H, Falbel T G, Durski A M, Vierstra R D
Cellular and Molecular Biology Program and the Department of Horticulture, University of Wisconsin, Madison, Wisconsin 53706, USA.
Plant Physiol. 2000 Dec;124(4):1828-43. doi: 10.1104/pp.124.4.1828.
Ubiquitin-specific proteases (UBPs) are a family of unique hydrolases that specifically remove polypeptides covalently linked via peptide or isopeptide bonds to the C-terminal glycine of ubiquitin. UBPs help regulate the ubiquitin/26S proteolytic pathway by generating free ubiquitin monomers from their initial translational products, recycling ubiquitins during the breakdown of ubiquitin-protein conjugates, and/or by removing ubiquitin from specific targets and thus presumably preventing target degradation. Here, we describe a family of 27 UBP genes from Arabidopsis that contain both the conserved cysteine (Cys) and histidine boxes essential for catalysis. They can be clustered into 14 subfamilies based on sequence similarity, genomic organization, and alignments with their closest relatives from other organisms, with seven subfamilies having two or more members. Recombinant AtUBP2 functions as a bona fide UBP: It can release polypeptides attached to ubiquitins via either alpha- or epsilon-amino linkages by an activity that requires the predicted active-site Cys within the Cys box. From the analysis of T-DNA insertion mutants, we demonstrate that the AtUBP1 and 2 subfamily helps confer resistance to the arginine analog canavanine. This phenotype suggests that the AtUBP1 and 2 enzymes are needed for abnormal protein turnover in Arabidopsis.
泛素特异性蛋白酶（UBP）是一类独特的水解酶，可特异性去除通过肽键或异肽键与泛素C末端甘氨酸共价连接的多肽。UBP通过从其初始翻译产物中生成游离泛素单体、在泛素-蛋白质缀合物分解过程中回收泛素，和/或从特定靶标中去除泛素从而可能防止靶标降解，来帮助调节泛素/26S蛋白水解途径。在此，我们描述了拟南芥中的一个由27个UBP基因组成的家族，这些基因包含催化所必需的保守半胱氨酸（Cys）和组氨酸框。根据序列相似性、基因组组织以及与其他生物体中亲缘关系最近的基因的比对，它们可被聚类为14个亚家族，其中7个亚家族有两个或更多成员。重组AtUBP2发挥真正UBP的功能：它可以通过一种需要Cys框内预测的活性位点半胱氨酸的活性，释放通过α-或ε-氨基连接与泛素相连的多肽。通过对T-DNA插入突变体的分析，我们证明AtUBP1和2亚家族有助于赋予对精氨酸类似物刀豆氨酸的抗性。这种表型表明AtUBP1和2酶是拟南芥中异常蛋白质周转所必需的。
