An FRT cassette separates the αTub84B promoter from sequence encoding full-length wts that is tagged at the N-terminal end with mTFP1 and at the C-terminal end with Citrine. mTFP1 and Citrine can act as a fluorescence resonance energy transfer (FRET) pair (donor and acceptor respectively), and this protein can act as a permuted wts FRET sensor: changes in the quenching ratio (acceptor channel emissions/donor channel emissions) can be used to monitor conformational changes in the wts protein in vivo.