The kinase activities of GST fusion proteins were measured in vitro.

A. Phosphorylation activities of GST fusion proteins containing full-length Stk (using plasmid pQG77), Stk^1–263 (pQG78) or Stk^40–263(pQG79) were measured with a Kinase-Glo™ luminescent kinase assay in vitro at 32°C for 4 h. B. Phosphorylation activities of GST fusion proteins containing full-length Stk (using plasmid pQG77) were measured with a Kinase-Glo™ luminescent kinase assay with or without staurosporine in vitro at 32°C for 4 h. GST was used as a negative control. RLU, relative luminescent unit. Data are derived from three independent experiments, **, P<0.01; ***, P<0.001 (versus GST).