Protein interaction domains in HIV-1 Vif. The regions responsible for interaction with A3G (red) and A3F (blue) are discontinuous. They overlap but are not identical. The region important for interaction with the Cul5 ubiquitin ligase complex is marked in green and includes a conserved histidine-cysteine-cysteine-histidine motif and a suppressor of cytokine signaling Box domain. The scale at the bottom indicates amino acid positions.