ubch-8

UBE2H is a member of the ubiquitin-conjugating E2 family whose members perform the second step in the ubiquitination reaction. Initially identified as the main process for protein degradation, ubiquitination is believed nowadays to be crucial for a wider range of cellular processes. The outcome of the ubiquitin-conjugation reaction, and thereby the fate of the substrate, is heavily dependent on the number of ubiquitin molecules attached and how these ubiquitin molecules are inter-connected. To deal with this complexity and to allow adequate ubiquitination in time and space, a highly sophisticated conjugation machinery has been developed. In a sequential manner, ubiquitin becomes activated by a ubiquitin-activating enzyme (E1), which then transfers the ubiquitin to a group of ubiquitin-conjugating enzymes (E2s). Next, ubiquitin-loaded E2s are interacting with ubiquitin-protein ligases (E3s) and ubiquitin is conjugated to substrates on recruitment by the E3. These three key enzymes are operating in a hierarchical system, wherein two E1s and 35 E2s have been found and hundreds of E3s have been identified in humans.

UBCH8, also known as UBE2L6, belongs to the ubiquitin-conjugating enzyme family. The family of ubiquitin-conjugating (E2) enzymes is characterized by the presence of a highly conserved ubiquitin-conjugating (UBC) domain. These domains accommodate the ATP-activated ubiquitin (Ub) or ubiquitin-like (UBL) protein via a covalently linked thioester onto its active-site residue. E2 enzymes act via selective protein-protein interactions with the E1 and E3 enzymes and connect activation to covalent modification. By doing so, E2s differentiate effects on downstream substrates, either with a single Ub UBL molecule or as a chain. UBCH8 is highly similar in primary structure to the enzyme encoded by the UBE2L3 gene. It catalyzes the covalent attachment of ubiquitin or ISG15 to other proteins. UBCH8 functions in the E6 E6-AP-induced ubiquitination of p53 TP53 and promotes ubiquitination and subsequent proteasomal degradation of FLT3. At protein level, it is present in natural killer cells.