TSG101(Tumor susceptibility gene 101) protein belongs to a group of apparently inactive homologs of ubiquitin-conjugating enzymes. This protein contains a coiled-coil domain that interacts with stathmin, a cytosolic phosphoprotein implicated in tumorigenesis. Mutations and alternative splicing in this protein occur in high frequency in breast cancer and suggest that defects occur during breast cancer tumorigenesis and/or progression. Recombinant human TSG101 protein, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography techniques.