In vitro radiolabeling autokinase activities of GST/(NΔ661)rJAK2 containing combinatorial cysteine-to-serine and cysteine-to-alanine mutations. Using immunoprecipitated recombinant GST/(NA661)rJAK2 variants produced in Sf21 cells, the autokinase activities of DTT-pretreated GST/(NA661)rJAK2, K882E, CC866,917SS, CC1094,1105SS, 4C:4S, CC866,917AA CC1094,1105AA and 4C:4A are shown in (A) lanes 1–8, respectively, and corresponding Western immunoblots probed with anti-JAK2 are shown in (B).