UASt regulatory sequences drive expression of a fusion protein composed of a truncated, constitutively active form of Src42A (amino acids 214-517, spanning the ATP-binding site and kinase domain, and containing a Y511F mutation in a crucial regulatory residue), the destabilized VHH(dGBP1) nanobody and a Tag:HA tag. The protein is designed to act as an engineered kinase; the VHH(dGBP1) nanobody should target the active kinase domain to proteins that are tagged with GFP (the target of the VHH(dGBP1) nanobody). In the absence of a GFP-tagged target, the nanobody is expected to be degraded.