Figure 4.
In vitro kinase activity of Tyk2 KL mutants. (A) Stable cell lines were untreated or treated with 103 IU/ml IFNα2 for 15 min. Tyk2 immunoprecipitates were then assayed for autophosphorylation (Tyk2) and substrate [glutathione S-transferase (GST)-IFNAR2] phosphorylation activities. (Bottom) The membrane was immunoblotted with an anti-Tyk2 antibody to determine protein levels. (B) Tyk2 proteins were transiently overexpressed in 11,1 cells and assayed for kinase activity, as above. The faint GST-IFNAR2 background band can also be detected in 11,1 immunoprecipitates.