Western blot of IFNAR1 from HEK 293 cells transfected with Mock (Lane 1), IFNAR1 WT (Lane 2), and IFNAR1 (S535A, S539A) mutants (Lane 3) . Specific immunolabeling of bands from ~110 kDa to ~130 kDa corresponding to Phospho-IFNAR1, (Ser535, Ser539) polyclonal antibody (Product # PA1-4627) is shown in the first blot (left), as the immunolabeling is absent in IFNAR1 Ser535 and Ser539 mutants (Lane 3). The specific immunolabeling is blocked by the phosphopeptide (+) used as the antigen in the second blot (right).