UBE2D4

UBE2D4 completes the UBE2D quartet and is the least studied member of the group. It retains the canonical UBC fold and active-site cysteine, is activated by UBA1, and collaborates with a range of RING and HECT E3 ligases in a manner overlapping its three paralogs. Expression is ubiquitous but generally lower than that of UBE2D1-D3, and functional redundancy among the four has hampered assignment of UBE2D4-specific physiological roles. Recombinant UBE2D4 is supplied mainly for comparative purposes: probing paralog preference of particular E3 enzymes, reconstituting polyubiquitin chain synthesis in vitro, and completing ubiquitin-pathway panels used in drug-discovery screening.