Kowalczyk Stanisław, Hadowska Emilia, Piekarska Anna
Department of Biochemistry, Nicolaus Copernicus University, 7 Gagarin St., 87-100 Toruń, Poland.
Postepy Biochem. 2005;51(2):171-87.
The general function of the ubiquitylation systems is to conjugate ubiquitin to lysine residues within substrate proteins, thus targeting them for degradation by the proteasome. In Arabidopsis thaliana more than 1300 genes (approximately 5% of the proteome) encode components of the ubiquitin/26S proteasome pathway. Approximately 90% of these genes encode subunits of the E3 ubiquitin ligases, which confer substrate specificity to the ubiquitin/26S proteasome pathway. The plant E3 ubiquitin ligases comprise a large and diverse family of proteins or protein complexes containing either a HECT domain, a RING-finger or U-box domain. The SCF class of E3 ligases is the most thoroughly studied in plants because some of them participate in regulation of hormone signaling pathways. The role of the SCF is to ubiquitylate repressors of hormone response (auxin, gibberellins), whereas in response to ethylene, abscisic acid and brassinosteroids the SCF participate in degradation of positive regulators in the absence of the hormone.
泛素化系统的一般功能是将泛素缀合到底物蛋白中的赖氨酸残基上，从而将它们靶向蛋白酶体进行降解。在拟南芥中，超过1300个基因（约占蛋白质组的5%）编码泛素/26S蛋白酶体途径的组分。这些基因中约90%编码E3泛素连接酶的亚基，其赋予泛素/26S蛋白酶体途径底物特异性。植物E3泛素连接酶包括一个庞大且多样的蛋白质或蛋白质复合体家族，其包含HECT结构域、RING指结构域或U-box结构域。E3连接酶的SCF类在植物中研究得最为透彻，因为其中一些参与激素信号通路的调控。SCF的作用是使激素反应（生长素、赤霉素）的阻遏物泛素化，而在乙烯、脱落酸和油菜素类固醇的响应中，SCF在缺乏激素的情况下参与正向调节因子的降解。
