Ubiquitin is a small protein that occurs in all eukaryotic cells. The ubiquitin protein itself consists of 76 amino acids and has a molecular mass of about 8.5 kDa. Key features include its C-terminal tail and the 7 Lys residues. It is highly conserved among eukaryotic species: Human and yeast ubiquitin share 96% sequence identity (1). The main function of Ubiquitin is to clear abnormal, foreign and improperly folded proteins by targeting them for degradation by the 26S proteosome (2). Ubiquitination represents an essential cellular process affected by a multi-enzyme cascade involving classes of enzymes known as ubiquitin-activating enzymes (E1s), ubiquitin-conjugating enzymes (E2s or Ubcs) and ubiquitin-protein ligases (E3s). Ubiquitin is activated in a two-step reaction by an E1 ubiquitin-activating enzyme in a process requiring ATP as an energy source. The initial step involves production of an ubiquitin-adenylate intermediate. The second step transfers ubiquitin to the E1 active site cysteine residue, with release of AMP. This step results in a thioester linkage between the C-terminal carboxyl group of ubiquitin and the E1 cysteine sulfhydryl group. The third step is a transfer of ubiquitin from E1 to the active site cysteine of a ubiquitin-conjugating enzyme E2 via a trans(thio)esterification reaction. And the final step of the ubiquitylation cascade creates an isopeptide bond between a lysine of the target protein and the C-terminal glycine of ubiquitin. In general, this step requires the activity of one of the hundreds of E3 ubiquitin-protein ligases (often termed simply ubiquitin ligase). E3 enzymes function as the substrate recognition modules of the system and are capable of interaction with both E2 and substrate(3, 4). Ubiquitination also participates in the internalization and degradation of plasma membrane proteins such as some of the TCR subunits while still ER-membrane associated (5). Ubiquitin also plays a role in regulating signal transduction cascades through the elimination inhibitory proteins, such as IKBA and p27 (6).
StressMarq Biosciences Inc. 在2007年成立于加拿大维多利亚，是一家生物科技公司，专门从事试剂与试剂盒研究，服务范围遍及2534多个国家。 StressMarq公司的核心技术领域为细胞应激（尤其是热休克蛋白（HSP）领域，领先全球），离子通道，载体研究，同时在神经科学领域推出特有的具有生物活性的Tau蛋白与A-突触核蛋白。产品领域涉及到：细胞凋亡、细胞信号、通路和转运、细胞器标志物、热休克、神经生物学、神经科学、氧化应激、磷酸化运输等。除了提供用于进一步研究的相关工具外，Str
