E In vitro phosphatase treatment of the THEMIS:GRB2:SHP1 complex. Bead‐bound THEMIS‐Strep complexes from 1G4‐CD8 cells were incubated in alkaline phosphatase (AP) buffer in the absence (lane 1) or presence of AP (lane 2), or left completely untreated (lane 3), prior to washing and elution. 