Figure 1.

Illustration of the SCF^skp2 complex. The SCF (Skp1–Cullin1–F-box) E3 ubiquitin ligase complex consists of four components: Skp1, Rbx1, Cullin1, and the variable F-box protein. In SCF^skp2, the F-box protein component is Skp2. Skp2 recognizes the targeted proteins and makes the ubiquitin transfer to the substrate protein by UBC (the E2 enzyme). The addition of polyubiquitin targets substrates for degradation by the 26S proteasome. The known substrates of Skp2 include p21, p27, p57, p130, Tob1, FOXO1, and c-Myc.