UBD, also known as Ubiquitin D, is an ubiquitin-like modifier (UBL) of the ubiquitin protein family. UBD is an ubiquitin-like protein that can form covalent conjugates, thereby targeting proteins for degradation by the 26S proteasome. UBD has putative roles in regulation of cell cycle, innate immunity, and apoptosis. UBD is a TNF-alpha-inducible ubiquitin-like protein with a putative role in immune response. Recombinant human UBD protein, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography.