The APOBEC3C crystal structure and the interface for HIV-1 Vif binding.

APOBEC3 (A3) proteins are cytidine deaminases that can restrict retroviral replication by causing hypermutation of the viral genome. The HIV-1 protein Vif counteracts the action of A3s by promoting their degradation. Now the crystal structure of A3C and homology models for A3F and A3DE, together with mutagenesis analyses, allow the identification of their interaction interface with Vif, which is different from a previously implicated region in A3G.