Structural Basis of Intermolecular Interactions Between APOBEC3 and HIV-1 Vif

The human APOBEC3 (A3) family of cytidine deaminases, including A3G, A3F, and A3H, participates in cellular anti-retroviral immunity. In contrast, to antagonize the anti-retroviral activities of these A3 family proteins, HIV-1 produces its gene product called viral infectivity factor (Vif) in infected cells. Vif is a pleiotropic hub protein that specifically binds to various A3 proteins with the aid of host core-binding factor subunit β (CBF-β) and mediates their proteasomal degradation. To date, numerous biological and structural studies have been performed to understand the arms race between A3 and Vif. Previous extensive mutagenesis and structural analyses have suggested that there are three distinct types of Vif-binding interfaces among human A3s and three largely nonoverlapping interfaces on Vif for binding with these A3s. Moreover, recent cryo-electron microscopy (cryo-EM) structural analyses have clarified further details of the different intermolecular interactions of Vif with each of three human A3s (A3G, A3F, and A3H) and have proposed a possible mechanism by which one Vif molecule can recognize all three types of A3s. In this review, we summarize the current understanding of the structural basis of the interaction between A3 and Vif. This information may be helpful for developing drugs targeting these interfaces.