Fig. 5

E28/L33 residues are important for binding of Vpu to BST2. a HEK293T cells were co-transfected with a proviral construct encoding WT Vpu or the indicated Vpu mutants and a BST2 expressor. Co-IP assays were then performed using an anti-BST2 Ab to pull down Vpu. Shown is a representative Western blot indicating the expression levels of proteins of interest in both the input lysate [actin (loading control), p55 (transfection control), BST2 and Vpu] and the immunoprecipitated fraction (BST2 and Vpu). b Co-IP following co-transfection of HEK293T cells with a proviral construct encoding WT Vpu or the indicated Vpu mutant and an expressor encoding for the short isoform of BST2 that contains the TMD involved in Vpu binding but is insensitive to Vpu-mediated degradation. Below each blot is the extent of BST2 binding of each Vpu mutant, relative to WT Vpu (set at 100%). For each condition, BST2 binding efficiency was determined from the ratio obtained from densitometric analyses of the intensities of Vpu- and BST2-related band signals in the immunoprecipitated fractions