Skp2 (S-phase kinase-associated protein 2; also F-box/LRR protein 1) is a 45-49 kDa member of the F-box protein family. It is known to be part of the SCF (Skp1/Cul1/F-box protein) complex. The SCF complex functions as an E3 ubiquitin-protein ligase that mediates the transfer of ubiquitin from an E2 enzyme to a target substrate. The specificity of the target is determined by Skp2. Molecules targeted for degradation include cell-cycle regulatory proteins that are involved in the G1-S phase transition. Human Skp2 is 424 amino acids (aa) in length. It contains one F-box (aa 94-140) followed by nine consecutive Leu-rich repeats (aa 142-369). There are two potential splice forms that contain substitutions for the same aa sequence. One contains a 4 aa substitution, while a second contains a 56 aa substitution for aa 354-424. Over aa 130-350, human Skp2 shares 84% aa identity with mouse Skp2.
