Ubiquitin-conjugating enzyme E2 B belongs to the ubiquitin-conjugating enzyme family and is encoded by the UBE2B gene in humans. The ubiquitin-conjugating enzymes, also known as E2 enzymes and more rarely as ubiquitin-carrier enzymes, take part in the second step in the ubiquitination reaction. In this reaction, E1 activates the ubiquitin by covalently attaching the molecule to its active site cysteine residue. The activated ubiquitin is then transferred to an E2 cysteine and then the E2 molecule binds E3 via a structurally conserved binding region. The ubiquitination reaction can modify proteins and regulate protein degradation. The UBE2B interacts with RAD18, UBR2 and WAC. Its protein sequence is 100 % identical to the mouse, rat, and rabbit homologs, which indicates that this enzyme is highly conserved in eukaryotic evolution.