Ubiquitin is a small protein that is composed of 76 amino acids and its sequence is highly conserved throughout evolution from invertebrates to mammals. In the cytoplasm, ubiquitin is involved in ATP-dependent nonlysomal proteolysis of various proteins. In the nucleus, ubiquitin is conjugated to histone2A and may play a role in regulation of chromatin structure and/or regulation of transcriptional activity. Ubiquitin(76amino acid) was overexpressed in E.coli and purified by using conventional chromatography techniques.