FIGURE 6.

CBFβ protects Vif from MDM2. A, surface model of the Vif-CBFβ heterodimer based on the reported structure of the Vif-CBFβ-ELOB-ELOC-CUL5 complex (PDB code 4N9F). Vif and CBFβ are shown in green and red, respectively. Vif R93 is highlighted in cyan, and APOBEC3G and APOBEC3F binding sites are marked in wheat and blue, respectively. B, proposed model in which CBFβ stabilizes Vif protein. Under normal conditions, CBFβ interacts with Vif extensively just near the MDM2 binding site and sequesters MDM2 from Vif. The Vif variant that is defective in CBFβ binding is preferentially captured by MDM2 and rapidly cleared by the proteasome pathway. Ub, ubiquitin.