UASt regulatory sequences drive expression of a fusion protein composed of a truncated form of Src42A (amino acids 214-517, spanning the ATP-binding site and kinase domain), the destabilized VHH(dGBP1) nanobody and a Tag:HA tag. The Src42A sequence contains two amino acid substitutions: a Y511F mutation in a crucial regulatory residue, and a K276M mutation that abolishes catalytic activity.