S-phase kinase-associated protein 1, also known as SKP1, is an F-box protein which functions as a substrate recognition component of the SCF ubiquitin ligase complex. It binds to proteins containing an F-box motif, such as cyclin F, S-phase kinase-associated protein 2, and other regulatory proteins involved in ubiquitin dependent proteolysis. It is also involved in the control of beta-catenin levels and the activity of beta-catenin dependent TCF transcription factors. Recombinant human SKP1 protein was expressed in E.coli and purified by using conventional chromatography techniques.