ubiquitination (泛素化，泛素化作用)

ubiquitination (泛素化，泛素化作用)

ubiquitination

泛素化

ubiquitination

泛素化，泛素化作用

ubiquitination (泛素化)

ubiquitin

泛素

ubiquitin

泛素蛋白

ubiquitin

泛蛋白

ubiquitin

泛素，泛素蛋白，泛蛋白

#

泛素化 (ubiquitination) 為一蛋白轉譯後的修飾作用，透過一系列之酵素將 泛素蛋白 (ubiquitin) 連接至 標的蛋白 上，以精確地調控細胞內蛋白質的功用並調控細胞內許多重要的生理功能。

#

The process of ubiquitination (or equivalently, ubiquitylation) typically requires three distinct biochemical activities (Figure 1). The first enzyme, E1, catalyzes ubiquitin “activation”, a term referring to adenylation of the ubiquitin C-terminal carboxyl group (Figure 2), and after ubiquitin transfer to a cysteinyl residue on E1, also refers to thioester-linked ubiquitin. Activated ubiquitin is transferred from E1 to a cysteinyl residue in a second protein called E2. Transfer of ubiquitin to substrate proteins typically requires a third activity called E3 or ligase. Depending on the E3, substrate ubiquitination occurs by direct transfer to the substrate from the E2 or after thioester formation of ubiquitin with the E3. Typically, ubiquitin forms a peptide bond with the ε-NH2 group on substrate lysyl residues termed an isopeptide bond, but more recently, ubiquitin ligation to the N-terminal α-NH2 group, or to serine, threonine or cysteine substrate residues forming peptide, ester or thioester linkages, respectively, with substrate proteins has been described in mammalian cells.

…

UBIQUITINATION ENZYMES

Ubiquitin activating Enzyme (E1)

…

First, E1 binds ATP, and then the AMP moiety of ATP is ligated to ubiquitin's carboxyl terminus, forming a ubiquitin adenylate that remains noncovalently bound to E1 and releasing pyrophospate. Second, ubiquitin is transferred to an active-site cysteine residue (半胱胺酸 殘留基), exchanging the high-energy acyl phosphate anhydride linkage with AMP for a thioester bond. AMP then leaves the enzyme. Third, while one ubiquitin remains thioester-linked to E1, another ubiquitin adenylate is formed, filling the ubiquitin adenylate binding site left vacant after step two. This third step is not intrinsically necessary for ubiquitin's activation, but under physiological conditions E1 exists primarily as a ternary complex of ATP, ubiquitin, and E1∼ubiquitin (Haas and Rose, 1982; Haas et al., 1982a; Haas et al., 1982b).

#