Figure 5
The (K395A/3F)Syk protein is enzymatically inactive Wildtype human Syk and (K395A/3F)Syk were transfected into syk-negative DT40 chicken B lymphoma cells and cloned. Syk kinase activity was evaluated by ICKA (upper panel) in extracts prepared from clones. The levels of wildtype human Syk and the (K395A/3F)Syk protein in the immunoprecipitate were also evaluated by anti-Syk immunoblotting (lower panel). Clones 5.1 and 5.2 represent two independent lines that express the (K395A/3F)Syk protein. The arrowhead marks the migration position of Syk. It should be noted that although these data indicate that mutant Syk is expressed in DT40 cells and that it is enzymatically inactive, expression of mutant Syk protein in BCL1.3B3 has not been demonstrated in these experiments.