SUMO3, also known as small ubiquitin-related modifier 3, is a member of the SUMO protein family and functions in a manner similar to ubiquitin. However, unlike ubiquitin which targets proteins for degradation, SUMO3 protein participates in a number of cellular processes, such as nuclear transport, transcriptional regulation, apoptosis, and protein stability. It regulates amyloid beta generation and may be critical in the onset or progression of Alzheimer's disease. Recombinant human SUMO3 protein, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography.