Ubiquitin conjugation factor E4 A (UBE4A)

Ubiquitin-protein ligase that probably acts as an E3 ligase in conjunction with specific E1 and E2 ligases. May also be the E4 ligase mediating the assembly of polyubiquitin chains on substrates ubiquitinated by another E3 ubiquitin ligase.

Mediates 'Lys-48'-linked polyubiquitination of substrates. .