SUMO-1, also known as small ubiquitin-related modifier 1, is a member of the SUMO protein family and functions in a manner similar to ubiquitin. However, unlike ubiquitin which targets proteins for degradation, SUMO-1 protein participates in a number of cellular processes, such as nuclear transport, transcriptional regulation, apoptosis, and protein stability. Recombinant human SUMO1 protein was expressed in E.coli and purified by using conventional chromatography.