Recombinant Vif mutants have a lower Cul5 binding affinity compared to wild-type Vif. Isothermal titration calorimetric analyses of the interaction between Cul5 and Vif wild-type and mutant complexes. A) and B) Representative ITC isotherm and table for Vif wild-type and mutants demonstrating a lower affinity between mutant Vif and Cul5 compared with Vif wild-type. C) Vif complex samples run on SDS-PAGE gel and visualized by coomassie stain and western blot. FL – full length.