In vitro binding of the hIL-5Rα cytoplasmic domain to JAK2. (A) GST alone, hIL-5Rα cytoplasmic domain fusion protein (GST-5RαCD), or βc cytoplasmic domain fusion protein (GST-BCD) were incubated with the cell lysates of unstimulated (−) or IL-5–stimulated TF-h5Rα cells, and the precipitated proteins were analyzed on SDS-PAGE and probed with anti-JAK2 Ab. (B) The deletion mutant (dDC1) and C-terminal truncated (TCD4, TCD2, TCD1-1, TCD1, and TCD0) GST fusion proteins were incubated with the lysates of unstimulated TF-h5Rα, separated on SDS-PAGE, and probed with anti-JAK2 Ab. The same amount of fusion proteins were separated on SDS-PAGE and stained with Coomassie brilliant blue (CBB).